Is there any *simple* way of getting a file's size, even if it is already open? I'm using this

Code:
Open f$ For Binary As #2
Size(J) = LOF(2)
Close #2
But, I get "Error 55: File already open" when it comes across files that are in use. I've looked at the GetFileSize and GetFileSizeEx API calls, and examples of how to use them, and I really don't wanna go through that much work just to get the file's size. I've also looked at GetFileAttributes, but that doesn't look any simpler. Any ideas?