Excel target speed calculator

I've put together a little spreadsheet for calulating target speed, does anybody know a way to upload the file if anybody wants it?

All it needs is:-

your current speed (knots)
initial bearing and distance to target (degrees & yards)
the time between sightings (seconds)
second bearing and distance to target (degrees & yards)


It will may need some testing, it's worked okay so far for me. (touchwood)