>>How about:
>>

>>IF TYPE(This.ControlSource)='C'
>>    if empty(This.InputMask)
>>       This.InputMask='!'+REPLICATE('X',LEN(EVALUATE(This.ControlSource))-1)
>>    endif
>>ENDIF
>>

>
>This.InputMask contains by default a value in the txtField class. I need to detect if at the form designer level, we have overwritten that value.

if dbgetprop('table_name.fieldname', 'field', 'inputmask') == This.InputMask
   *** then you have not overwritten the input mask
else
   *** the input mask ws changed
endif