custom editors in ss 2005

I'm trying to use WinMerge as my custom editor and can't get it to
find the file on the server. It just finds the local files. Here's
what I put in the Custom Editors area........

File Difference
..*
"C:\Program Files\WinMerge\WinMergeU.exe" %1


I have tried a variety of them but none work.
"C:\Program Files\WinMerge\WinMergeU.exe" %1 %2


"C:\Program Files\WinMerge\WinMergeU.exe" %1% %2%


My server file is referenced as:


$/myfolder/myfile.js


Thanks for any tips