We have created a new pushbutton in a certain screen. The function code "BACK" carried out by the pushbutton is a so-called "Exit command" in SAP that does not check the entered values. But when the user presses our own pushbutton, the values are checked. 
How can we achieve exactly the standard behavior of the SAP key?

Instead of using the function code "BACK" in the pushbutton definition, please use the function key, i.e.

Pushbutton (10,12)   "Exit"   "/3"