Code to check wether a file is already open

Hello experts

I am attaching herewith 2 files . One is monthly and other one is yearly.

What i am doing is this :
in monthly file I have 3 command buttons.
1 to delete records where tonnage is zero
2 to transfer(copy & paste) monthly records to yearly file
3 to delete records from the monthly file.

every thing is working fine except that in command button 2 i want to check wether yearly file is already open.
if it is open proceed further
if it is not open, open it and proceed further.

any help ?

kmahesh