Another button to improve

So following the advice of the experts in the forum, I came up with this master of buttons.
three-function button
LMB opens drive in left
RMB opens drive in right
MMB ejects the drive
I was wondering, though, if there was some technique which would make this button invisible when the m: drive is actually not present?

like the way a real drive button would behave?

<?xml version="1.0"?> <button backcol="none" display="label" textcol="none" type="three_button"> <label>M:</label> <icon1>#newcommand</icon1> <button backcol="none" display="label" textcol="none"> <label>M:\</label> <icon1>#newcommand</icon1> <function type="normal"> <instruction>go m:\ OPENINLEFT/S</instruction> </function> </button> <button backcol="none" display="label" textcol="none"> <label>Right</label> <icon1>#newcommand</icon1> <function type="normal"> <instruction>go m:\ OPENINRIGHT/O vert</instruction> </function> </button> <button backcol="none" display="label" textcol="none"> <label>Middle</label> <icon1>#newcommand</icon1> <function type="normal"> <instruction>D:\My Dropbox\--- Apps ---\--- Eject, Remove Drives ---\x64\RemoveDrive.exe M:\</instruction> </function> </button> </button>
M;.dcf (875 Bytes)