When the user imports a video clip, please run a check of
Session setup window-->Timecode Rate against the frame rate of the video clip.
If there is a mismatch, then display a warning that effectively says "The frame rate of the video you have imported does not match the timecode rate of your session. What would you like to do?" The two clickable buttons are "Ignore" and "Switch the timecode rate to match video clip". The default is "Switch the timecode rate to match video clip".