Sorry Enjay.
I'm not getting it.
I don't understand what it is you are wanting.
Wait till Shaun rolls up - he pretty clever at this stuff.

All I can say is
if you put "=MAX(L:L)" into say Cell M1 , it will tell you the Peak your Bank has ever reached.
Then if you want say 10% of that , you can put say "=M1/10" into cell M2
I would like to help but my head hurts.