Archiving with relative pathes only

Hi all,
I compress the folder contents recursevely (except files with psd extension)

do shell script "zip -r " & toFile & " " & myFolder & "-x \\*.psd"

but it stores full pathes, not relative to the myFolder
Is any way to store only relative pathes?

If I use

do shell script "/usr/bin/ditto -c -k -rsrc --keepParent " & quoted form of myFolder & " " & quoted form of (myFolder & ".zip")

it stores relative pathes,
but it seems that ditto has no switch to exclude user defined filenames