Transaction button not working

Hi all,

I am using Screen personas 3.0 i want to create a transaction button with code '/OSMEN'(/O  for opening in new session) but it is not allowing me to enter '/O' IN TCODE of button definition so how can i use '/O' in tcode ???
and can we have any other way to open a transaction in new session with transaction button??

Help me out in this case!

Thanks & Regards,

Nishanth .B