Hi All,
Thanks for all the replies - but maybe I should start from scratch and
explain the question in, hopefully, a clearer way [ sorry if I confused
everyone]

In A1 I have '=Countif(B1:B500,15)'

The integer values in cells B1:B500 get incremented with each sheet recalc
due to random functions elsewhere in the sheet and therefore A1 is
incremented randomly with each recalc.

The macro is required to recalculate the sheet until A1 = 'exactly' 100. -
i.e when there are exactly 100 cells in B1:B500 with a value of 15.

So I wrote

Do Until Range("a1") = 100
' Do Stuff
Calculate
Loop

The problem is that A1 can be incremented in irregular steps - e.g. from 1
to 2 to 6 etc. and from 93 to 94 to 99 to 102 etc. and therefore a1=100 is
never true - hence a permanent loop

But I need to restart the Do Until loop if and when A1 exceeds 100.

[BTW I can handle the resetting of the values in B1:B500 with a small
routine between 'Loop' and 'End']

Thanks again
Jack