many thanks to Luke for a quick and informative answer. It gives me the basis
of what i want. What i should have said is that the ages of the children need
to be in years and months (or simply months) so that a more exact measure can
be provided between age and assessed age. I could simply type in the months
as a figure after working it out separately but i have been trying the year
and month functions to do it for me and not quite getting it right. if i
could and then fit it into lukes solution i think i may have it. EG. Child
born on say 01/01/2000 takes a test on 03/03/2009 and gets an assessed
reading age of 8 years 2 months (actual age 9 years 3 months). Next test is
on 04/03/2010 and he/she gets 10 years 2 months assessed age ( actual age 10
years 3 months) so the child has improved and the measure of the improvement
is the change in the difference between actual and assessed year on year Can
you help further