[TextMate] Custom Shell Variables question

[Mats Persson]

OK, I might be opening my mouth and removing all doubts about my 
stupidity here, but I can't think of a solution to this problem, so 
here goes..

I have a project in the following location:  [  
/Users/mats/Sites/projectName/  ]

In my template I use Custom Shell variables to auto-enter the relevant 
info.

The "TM_FILEPATH" returns: [  
/Volumes/WorkDisk/Users/mats/Sites/projectName/index.php  ]

*but* I would prefer to have:  [  /projectName/index.php  ]

in other words remove [ /Volumes/WorkDisk/Users/mats/Sites ] from the 
TM_FILEPATH  or alternatively create a new shell variable with this 
info only.

I guess that I would use some form of 'grep' and remove the bits that I 
don't want, but I can't work out how.

Any help would be greatly appreciated.

Kind regards,

Mats