To start, see this thread with many examples of scripted finds--including some that use calculated date ranges.
If that's not enough to get things working, feel free to use Post A Answer to post back to this thread and we'll take a closer look at what you are trying to do.
I've looked at all those and they aren't close to what I need, AND I can't seem to connect the dots using those methods to get to something that does work. Thanks.
I think that they are exactly what you need, but you need to add in additional details to get from the menu selection to the specified date range criteria. The examples show how to produce the needed criteria.
Partial script example:
Say you define a global text field, gRangeOption, with a value list of your date range options: "This Week", "This Month", "Last Month" and a pair of global date fields, gDate1, gDate2, for specifying an arbitrary date range:
Enter Find Mode 
If [IsEmpty ( Globals::gRangeOption ) // user didn't select a range option, check for arbitrary date range ]
If [ Not IsEmpty ( Globals::gDate1 ) and Globals::gDate2 > Globals::gDate1 //valid date range was entered ]
Set Field [ YourTable::YourDateField ; Globals::gDate1 & "..." & Globals::gDate2 ]
Enter Browse Mode 
Show Custom Dialog ["ERROR: No valid search criteria was entered"]
Else IF [ Globals::gRangeOption = "This Week" ]
Set Field [YourTable::YourDateField ; Let ( [T = Get ( CurrentDate ) ; D = T - DayOfWeek ( T ) ] ; D + 1 & "..." & D + 7 ]
Else If [ Globals::gRangeOption = "This Month" ]
Set Field [YourTable::YourDateField ; Month ( Get ( CurrentDate ) ) & "/" & Year ( Get ( CurrentDate ) ) ]
Set Field [YourTable::YourDateField ;Year ( get ( CurrentDate ) ) ]
Set Error Capture [on]
Perform Find 
About global fields:
Fields with global storage specified in field options may be defined in any table in your database file and they will still be accessible to any script and on any layout in your file. I prefer to define all such global fields in their own globals table unless they serve as a match field in a relationship.
Unlike non-global fields, the values in global fields remain accessible when the current window enters find mode. Thus, the above script will not work as written unless the fields referenced in the IF steps and the second parameter of the first Set field step are defined to use global storage.
Plil, you are correct. Now let me see if I can figure out how to get that done. Thanks so much!!