Yeah I have just tried the GoalSeek too and it works. You just apply it to the start time and it does it all for you, so long as you have the formulae sorted correctly. Simples! 1) 12 Noon arrival does not go red with the conditional formatting, therefore must be OK, however, I can see them saying that students need to allow some contingency time in? 2) my error I had read it as would need to collect 2 lots of 30, hence 4 coaches with a capacity of 15. 3) I assume you mean row 17?? Looks to be where a formula needs be entered in C17 and D17 where there is no need for a minibus to stop. If you enter anything in there however it affects everything in the hidden columns I to N and messes up the figures in B21 to B25 4) I like that way. Will see which my students grasp the best of the three.