Thanks for getting back to us.
As far as I understand you would like to double check if a file is currently opened. If so please note that this should be accomplished with a coded solution which would be subject of general C3 programming approach and could implemented in a coded step.
I searched the web for some advice and here is a forum post
which might be useful to suit your needs along with details from MSDN about the FileStream Class
and FileStream Constructor
I hope these will be helpful! Thank you for your cooperation!