How to Detect Google Calendar Room Booking Conflicts in Slack with Make

Dashboard > Create new scenario

Create New Scenario

Start a fresh scenario in Make to build your room conflict detection workflow. The scenario will run every 15 minutes to check for overlapping events.

1. 1Click 'Create a new scenario' from your Make dashboard
2. 2Select 'Start from scratch' instead of using a template
3. 3Name your scenario 'Room Booking Conflict Detector'

Scenario > + > Google Calendar > Watch Events

Add Google Calendar Trigger

Connect Google Calendar as your trigger to watch for new or updated events. Use the 'Watch Events' trigger to catch any calendar changes in real-time.

1. 1Click the gray circle to add your first module
2. 2Search for 'Google Calendar' in the app list
3. 3Select 'Watch Events' as your trigger type
4. 4Connect your Google account when prompted

Google Calendar module > Settings

Configure Calendar Selection

Choose which calendar contains your room bookings and set the polling frequency. Most companies have a dedicated room or resource calendar separate from personal calendars.

1. 1Select your room calendar from the 'Calendar ID' dropdown
2. 2Set 'Limit' to 50 to catch multiple simultaneous bookings
3. 3Choose 'Updated Time' for the 'Order By' field
4. 4Set polling to every 15 minutes

Scenario > + > Tools > Iterator

Add Iterator Module

Add an iterator to process multiple calendar events individually. This lets Make check each event against all others for time conflicts.

1. 1Click the + button after your Google Calendar module
2. 2Search for 'Tools' in the module list
3. 3Select 'Iterator' from the Flow Control section
4. 4Map the 'Array' field to the calendar events bundle

Scenario > + > Google Calendar > Search Events

Add Second Google Calendar Module

Create a second calendar connection to search for overlapping events. This module will find other events that conflict with each event from the iterator.

1. 1Add another Google Calendar module after the Iterator
2. 2Choose 'Search Events' as the action
3. 3Use the same calendar as your trigger module
4. 4Set 'Single Event' to No to return multiple results

Google Calendar Search module > Settings

Configure Conflict Detection

Set up the search parameters to find events that overlap in time with the current event. Use start and end time filters to catch any scheduling conflicts.

1. 1Map 'Time Min' to the current event's start time from Iterator
2. 2Map 'Time Max' to the current event's end time from Iterator
3. 3Set 'Max Results' to 20 to catch multiple conflicts
4. 4Add 'Single Events' set to true

Module connection > Filter

Add Conflict Filter

Create a filter to only proceed when actual conflicts exist. The filter checks if the search returned more than one event for the same time slot.

1. 1Click the wrench icon between Search Events and the next module
2. 2Set condition to 'Total number of bundles'
3. 3Choose 'Greater than' as the operator
4. 4Set the value to 1

Scenario > + > Tools > Array Aggregator

Add Data Aggregator

Use an aggregator to collect all conflicting events into a single message. This prevents sending multiple Slack notifications for the same conflict.

1. 1Add an 'Array Aggregator' module after the filter
2. 2Set 'Source Module' to the Google Calendar Search
3. 3Map the 'Value' field to event summary and time
4. 4Choose 'Text' as the aggregation type

Scenario > + > Slack > Send a Message

Connect Slack Module

Add Slack to send conflict notifications to your office channel. Use 'Send a Message' to post details about the booking conflict.

1. 1Add a Slack module after the Array Aggregator
2. 2Choose 'Send a Message' as the action
3. 3Connect your Slack workspace when prompted
4. 4Select your #office channel from the dropdown

Slack module > Text field

Format Conflict Message

Create a clear message template that shows which room is double-booked and when. Include event names and organizers so conflicts can be resolved quickly.

1. 1In the 'Text' field, write: '🚨 Room booking conflict detected!'
2. 2Add event details using mapped fields from the aggregator
3. 3Include start time, end time, and event titles
4. 4Add 'Please resolve ASAP' at the end

📬 New entry: {{1.name}}
Email: {{1.email}}
Details: {{1.description}}

Scenario settings > Advanced settings

Add Error Handling

Configure error handling to prevent the scenario from breaking when API limits are hit or connections fail. Set up retry logic for temporary failures.

1. 1Click the scenario settings gear icon
2. 2Enable 'Sequential processing' to avoid rate limits
3. 3Set 'Max number of cycles' to 1 per execution
4. 4Turn on 'Store incomplete executions' for debugging

Scenario > Run once > Toggle ON

Test and Activate

Run a complete test with real calendar data to verify conflict detection works correctly. Check that the Slack message format is clear and actionable.

1. 1Click 'Run once' to test the entire workflow
2. 2Create a test conflict by booking the same room twice
3. 3Verify the Slack message appears in your #office channel
4. 4Click the 'ON' toggle to activate the scenario

Drop this into a Make custom function.

{{if(contains(1.location, "Conference"); "🏢 "; if(contains(1.location, "Phone"); "📞 "; "📅 "))}}{{1.location}} conflict: {{1.summary}} ({{formatDate(1.start.dateTime; "h:mm A")}}-{{formatDate(1.end.dateTime; "h:mm A")}})

{{if(contains(1.location, "Conference"); "🏢 "; if(contains(1.location, "Phone"); "📞 "; "📅 "))}}{{1.location}} conflict: {{1.summary}} ({{formatDate(1.start.dateTime; "h:mm A")}}-{{formatDate(1.end.dateTime; "h:mm A")}})