Hi guys I have this remote for my D90 - it's a Phottix TC501 (the one that has timer controls). I must be dumb but after trying hard for the last 5 days coul dnot open the battery compartment to change the battery. I have tried taking the screws out - that did not work. Tried opening the part which shows an arrow (even with a screw driver that has now left marks) but coul dnot open it - any ideas please