Ok, here we go. This will work, it�s native and you can set it up in 15 minutes.
One Service has Many Time Entries.
Create a Summary field of the Minimum Date. Call it [Service Date 1]
Lookup [Service Date 1] down to Time Entries.
Because we are lazy, Duplicate the Summary field but this time add a filter [Date] > [Service Date 1], and call it [Service Date 2]
Lookup [Service Date 2] down to Time Entries.
Because we are lazy, Duplicate the [Service Date 2] Summary field to similarly make [Service Date 3]
So let�s say you now have 10 of them. Some will be null if there�s less than 10 unique dates.
So the final answer is the number of non null dates.
Count(
not isnull([Service Date 1]),
not isnull([Service Date 2]),
not isnull([Service Date 3]),
Etc
not isnull([Service Date 10]))
