hmmmm bit hard to describe...

but let me try to clarify....

I have a list of around 9000 numbers - the numbers represent groups of part numbers for ordering parts...

out of this list only around 2000 numbers are in use.... but they are randomly used...

i.e. 8001 may be in use... 8003 8051 7999 etc may be free to use.

out of this list I need to find a reasonable amount of 'free' numbers. but they need to be in sequence...

i.e. I need to say... groups 2010-3050 or 1500-1600 etc are free to use.
(but if any number between those two limits is used then I cannot use those batches)

it will take me ages to manually go through 9000 numbers looking for the greatest uninterrupted sequence... so I wanted to do it with a formula?? im close but not there yet!! lol

you can add whatever columns or do whatever with the data - im only using excel to try to save doing it manually.

any clearer?