Another way to achieve this without using a helper column is to type
100 into a blank cell somewhere. Select this cell again and click
<copy. Then highlight all the cells which you would like to convert
and click Edit | Paste Special | Values (check) and Divide (check) then
click OK. This will convert all your values, and while the cells are
still highlighted, then you can click Format | Cells and apply your
currency format.

Hope this helps.

Pete