I am trying to calculate the control source based on data. Perhaps I am not even using the correct tool? Both data fields are defined as date.

* This one does not work!!(-245820) answer when a valid date is enterd.

if ((year(apptrack.issueprmt)>1) .and. (year(apptrack.noprmdte)< 1))
THIS.CONTROLSOURCE="0+int(val(SYS(11,apptrack.issueprmt)) - val(SYS(11,APPTRACK.APPRECVD)))"
endif
* This one does work!!
if ((year(apptrack.noprmdte)>1) .and. (year(apptrack.issueprmt)< 1))
THIS.CONTROLSOURCE="0+int(val(SYS(11,apptrack.noprmdte)) - val(SYS(11,APPTRACK.APPRECVD)))"
endif

Can someone put me on the correct path! Thanks!