Thanks for both your help!

Del Cotter i've got your method working nicely now for highlighting all
values that are within +- 25cm using the formula:
=IF(C40.25,NA(),IF(C4<-0.25,NA(),A4))

Where A = first elevation, B = Second elevation & C = difference between the
two.

i've also done this for +- 50, 75, 1 and 1m

the only problem is that it also selects all values before it as well (ie
all the +- 25cm results are also in the +- 50cm table) i'm now trying to get
another formular to seperate these results for me but i'm having some trouble
do you have any ideas?

i'm using these and they don't seem to work:
=IF(AND(C14<0.5,C140.25),AND(AND(C14<-0.25,C14<-0.5),"output_1","output_2"),"output_3")
=IF(AND(C14<0.5,C140.25),IF(AND(C14-0.25,C14-0.5),"output_1","output_2"),"output_3")

i've uploaded the file incase anyone wants to take a look.
http://www.filefactory.com/file/5f8d3a/

many thanks in advance :)