What are the minimum and maximum times you will be needing to measure?

Will you be needing anything else going on at the same time?

Maybe something like
Code:
for X = 1 to 255
pause 10
t = t + 1
do whatever, pot
if whatever =  thisorthat then tCalc
next x
tCalc:
display t
I know, not real code But an idea for you to try.

So if "t" equals 100 , that would mean about a second has passed.