Hi Gordon,
I have not tried SP, as I read that it is triggered only on Form Submit.
As I posted in my other thread in the SDK forum (http://scn.sap.com/thread/3458442): if I have a row level UDF which is mandatory in certain conditions and there are certain calculations based on the UDF and user should not be able to move to the next field or next row without inputting value in that UDF, then SP will not help. Note that the UDF is not mandatory in all conditions, hence probably SDK is required.
