Can anyone help ?

We have a macro that amongst other things formats cells
which runs using excel 95 - however when we run this
macro using excel 98 or higher we have noticed a
considerable increase in the length of time taken to
complete the run. Is this due to the vast increase in
the number of cells it might have to format in the later
versions of excel or is it a change in the vba itself?

Many thanks
KD