Modules & VBA :: Command To Execute When Form Is Closed Or Quit

There is a form where whenever the form is closed, the below code needs to execute:

If IsNull(Me.CostPerPiece1.Value) = True And IsNull(Me.CostPerPiece2.Value) = True And IsNull(Me.CostPerPiece3.Value) = True And IsNull(Me.CostPerPiece4.Value) = True And IsNull(Me.CostPerPiece5.Value) = True Then
Me.AllowAdditions = False
DoCmd.SetWarnings (0)
DoCmd.RunCommand acCmdDeleteRecord
DoCmd.SetWarnings (-1)
Else
Call AppendQuoteCharges
End If

The If Then just looks at if certain fields are all null and if so, it deletes the current record. If at least one field is not null, the AppendQuoteCharges routine is called.

The form has 4 or 5 navigation buttons that close this form and send you to a different one. I've added the above code to each of those buttons before it runs the DoCmd.Close Form. I also have a Exit button that runs a DoCmd.Quit. I developed this months back but I'm pretty sure I added the above code under each button's click event rather than a Form On Close event because Form On Close does not execute after a DoCmd.Quit command

In rare cases, the form is being closed without the routine being ran. I think if a user clicks the Close button in the top right of Access (the X), it might be running a DoCmd.Quit which is doesn't run this code.

How can I be sure that whenever the form is closed or exited, the code is ran? Is there a way to tie this code to the user clicking the X in the top right?