Adding own option to peer menu - what is the correct syntax?

I am trying to add the RDP command (mstsc on WIndows) to the right-click menu. I seem not to be able to figure out the correct syntax..

Anyone can help?

I tried 

mstsc /v:$VIP

mstsc /v: $VIP

c:\windows\system32\mstsc.exe /v:$VIP

c:\windows\system32\mstsc.exe /v: $VIP

All I get is the Usage window one can trigger with something like "mstsc /"

Thanks

Dan

Gui.ConfirmEvict 1
Gui.CustActCmd mstsc /v:$VIP
Gui.CustActShow 1
Gui.CustActTxt RDP
[...]

Peer.LabelConn $NICK - $VIP
Peer.LabelDisc $NICK
[...]