WF4 macro for open automatically .drw

I want to make a macro for automatically  open files .drw when i have in the monitor the relative files .prt or .asm.
The function must work on the currently workspace.
The problem is how to have the name of the file in the monitor.
Exist a label /dependent variable that return the name of the open's file ?
&dwg_name not works in the macro.
This label must change and must be the name of the open's file .

Thanks