@snow_beginner 

create a custom flow action, accept 1 string as input and other input as table name, have output as count

In that flow action, you can use script step and use GlideRecord and encoded query (use the condition passed as input), set the count as output variable

you will have to use Lookup Records on that table and then call that flow action, then use IF logic to know the count and based on count 0 or more than o you can update that checkbox

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