While it is theoretically possible to do this, the fact that you have a front-end open very often means that the back-end is also open. Normally, you will require exclusive access to the BE to do a Compact & Repair. If even one other person has the FE open, you will NOT be able to do this at all. Even if they aren't doing anything, having the BE open by two users is enough to deny lock conversion from Shared to Exclusive. Without that lock conversion, you are dead in the water.
The way that I always did this was that we had a time set aside every other week so that we could take down the DB completely in order to manually perform the C&R.