SQL2k sp4a / Windows 2003

I have a DTS package that imports text files from a directory. These files
are ftp'd to us by a customer, so we never knew when they will be coming in.
Before we import the file, we need to determine if it's in use - which means
the customer is in the process of ftp'ing it.

Is there a way in ActiveX that I can determine if the file is in use?

Thanks in advance.

Andre