hmmm, I am wondering if it has to do with the lack of IF in front of the not IsUserEmail.
Maybe it should look more something like...
If([End Time]<[Start Time], "End Time cannot be before Start Time",
//else if
if([End Time]=[Start Time], "End Time cannot be the same as Start Time",
//else
////separate out both statements with parenthesis
if(((not IsUserEmail("david@example.com")) OR (not IsUserEmail("jason@example.com")))
AND ([Date]>[Test Date] OR [Date]<[Test Date]-Days(7)),"Date must be in current work week")))
//the final parenthesis close all three if statements.
including all of these if statements is not necessary, but may make it easier to see where you are getting hung up.
I do want to note, I would make this a formula text field at the table level, add it to the form, and based on the response, a form rule should prevent you from saving, instead of a Custom Data Rule. That way this field can be used on reports as well as other formula fields.
thanks
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Ursula
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