SaveFileDialog intercept file select

I'm running into an issue someone more experienced with C# tools development might be able to help with. I'm currently using the Windows SaveFileDialog to allow users to select a file to save as, and currently it throws up an error for a file that is readonly before it processes the FileOk event.

I'd like to be able to intercept the file name before it does any checks and as a blocking operation (with a time out) communicate with our Perforce repository to check the file out which would remove the read-only state.