App-Open callback example

Anyone have an example of callback to the original form in an app-open slider?
I have a layer for ReportQty that calls some functions etc on the slider. I can hook to the OK button event to finalize everything, however, the Cancel button has no event to hook to.
I am going to try the slider OnCancel to perform a function if they hit cancel.
I need to pass callback on piece of data to use in that function after the OnCancel.

I am trying to figure out the value out or another method to callback from the child slider to the main MES screen.