You have a few options here. Simplest/best I’d say: do an [B]Open…[/B] on a “file:” comm handle. (Perhaps followed by a [B]GetNumCharsWaiting [/B]to get the file size, in case a 0 for that means “doesn’t really exist” for you.)
Fancier method if you’re using lots of different files and need a listing, would be to use an “ftp:” comm handle, specifically the “dir” option with [B]SendCommunicationHandleCommand[/B].
BTW, also check out the [B]GetAvailableFileSpace [/B]commandwhich you can use to keep track of how much file space you have remaining in your on-board RAM, flash, or microSD card. Happy “filing”!