Hi

I'm looking for a formula that will automatically calculate the amount of time required over a term.

Value in the 1st month will be at its highest, subsequent months should reduce by 10% on the previous month ideally to a floor value per month e.g.

M1 10
M2 9
M3 8
M4 7
M5 6
M6 5
M7 5
M8 5

the floor would be 5 but I'd like to set the monthly reduction to be a % rather than the -1 i've used above.

Any ideas very welcome

Thanks

Dave