If Field 2 is to be yes if Field 1 has any value whatsoever, simply set Field 2 to be a calculation (result is Text) with the formula:
Case (IsEmpty (Field1) ; "" ; "Yes")
That it is a checkbox is in the layout formatting on the Data tab.
When the layout is opened both fields are blank. I need to be able to make field 2 "yes" manually by clicking on it as well as automatically by entering data in field 1. Sorry for the confusion.
Ahhh, manually too...
Make a script :
If (not Isempty(Field1) )
SetField (Field2 ; "Yes")
Launch the script OnModify based on Field 1.