Phew!

I seem to have cured this problem. Consider the following:

Code for IRChange() of combo:

With Thisform
  .txtRoute.Value	    = this.value
  .txtRoute.refresh()
  .cRouteNo	    = this.value
  .cDirectn	    = this.List( this.ListIndex, 3)	&& Directn is 3rd in list
  .txtDirectn.value   = .cDirectn
  .txtDirectn.refresh()
  .cmdPrint.enabled   = .T.
  .cmdPreview.enabled = .T.
EndWith

Having selected from the list box, the accompanying text box, .txtRoute, is assigned the value from the list box, taken from the select cursor/table. Now, whilst writing the form, I'd set its ControlSource to ROUTE.Route (its PK), but now I was "overwriting" it with the cursor's .Route (taken from select of the Route table). No immediate complaint from the form though, until I click the preview button. As I said in the orig message, the error was popping up somewhere between the two events, but not where it could be trapped. Strikes me that somewhere it should have said it didn't like it.

Anyway, I cleared the text box's ControlSource and now don't get the error. Still don't understand why the message only happened on certain records and why in such a strange manner.

Terry