I just created a text box on a form. then insted of toolbar, i created a button with code SYS(1500,"_med_undo","_medit") (same code for undo button).
After that i run the form. If i write something in that form, By pressing Ctrl+Z (Undo) it clears whatever i have written. But insted i press that undo button, It doesnt clears the text box. this code work with tool bar.