Ok Im trying to sych the form payments history to reflect the current record that is open in another form but I can't figure out why this function is not working here's my code
If IsOpen("Debtor_Window") Then
DebtorID.DefaultValue = FormsDebtor_Window!Debtor_ID
End If

As I am sure you are aware the IsOpen function is not a standard function in Access and needs to be included in a module by the db creator. If it isn't working because it's saying it doesn;t recognise the user defined function then I would look at the Northwind database which should be in your samples directory and import the IsLoaded function from that db. Then use IsLoaded in place of IsOpen.

HTH