Editable ALV problem with CHECK_CHANGED_DATA

Hi. We've found a problem that is probably easy to fix, but I can not find a post on SDN about it.

If we have bad data in our editable ALV and call method CHECK_CHANGED_DATA importing E_VALID it correctly gives us error messages on screen and E_VALID is initial where fields do not exist in their check tables.

However, if we press save again without changing any more data then CHECK_CHANGED_DATA does not issue errors and E_VALID = X.

It is only checking data that we have changed since the last time the method was called. If a user presses save twice it gets past the error messages.

We could obviously put checks in the PAI the screen but that would mean putting in our own code when SAP is supposed to do it on its own.

Does anyone know how we can make it check the data and issue messages every time you press save?

Thanks a lot for your help.

Regards,

Dave.