simulate leveladjustment in a watertank.

I have a problem which probably is very simple, but Im not able to
solve it right now. I want to divide a value that the user shall input,
to use in a program which is supposed to simulate leveladjustment in a
watertank. The problem is that the user must be able to input a value
between 0 and 40, and the value has to be written like a vertical
column. To make room for it on the screen I have to divide it. Hope you
understand what Im trying to say!?
Hopeful for answer,
Claes