I have a sheet that will potentially use all 60 odd thousand rows. One column
will be "Job" and I want a list of unique jobs to be generated from this
column.

Currently I'd have a countif along the lines of
=IF(COUNTIF($A$1:A13,A14)0,"",MAX($B$1:B13)+1)
copied all the way down, then use the numbers to index/match and pull off a
list of jobs.

To have this running down the entire sheet would take a bit of processing
power (maybe not alot, but certainlly more than I want it to if possible) and
it occurs to me that if I could find a formula that finds the next unique
match in an array (compaired to another array) that this would help lots.

=VLOOKUP(<A1:A10,Sheet1!A1:A65536,1,FALSE) for example.