I have a subform that I place this code in BeforeUpdate:
If MsgBox("Do you want to save? (click 'No' to undo)", vbYesNo, "Save") = vbYes Then
DoCmd.DoMenuItem acFormBar, acRecordsMenu, acSaveRecord, , acMenuVer70
This works because the form is a single form. I also have a continuous subform on the main form that I want to apply the same technique. But because there could be more than one record entered, I'm not sure how to apply this.