Trapping on the "Add" message box

Hi,

I am trapping an event on the Add button of a document but before I add, I need to check something, but I need it to be after the following message box appears…

You cannot change this document after you have added it – continue?

and before the document is added to the database.

Using pVal.Action_Success as not true is too early and when it is true is too late.

Any help appreciated,

Robin