Software Problem

We have a piece of software that is based around MS Access 97 I am having a problem with it. When I log Into the software and go to - DATA MAINTENCE MENU - ITEMS to open a form and change the anount of items etc in the product database (this is when the error happens) The Error that pops up on screen is: The Expression On Click You Entered As The Event Property Setting Produced The Following Error: THE OPEN FORM ACTION WAS CANCELED. * The expression may not result in the name of a macro, the name of a user defined function, or [event procedure]. There may have been an errorevaluating the function, event or macro. Has anyone any Ideas how to fix this error? We required it fixed.