is there a formula for this (when working with 2 tabs)

here is an example of the problem (obviously limited due to confidentiality)

it would be much appreciated if you would take a look and if you or anyone else knows if it is possible to do what i hoped to do

kind regards

is this what you mean?

example of problem.xls

Wow.. I think that is exactly what I mean!

Shall just try it on the actual sheet!