How to change activesync My Files sync to storage card?

[Guest Dr Who]

I thought I would trying using the activesync My Files sync function to throw a few music files onto my phone. It managed to put about three on there before the phone gave me a low storage warning, and lo and behold they were synced to the phone storage and not the storage card. So I had a look about and I can't see any way of changing the location of the activesync My Files directory on the phone side. Anyone know how I can do this?