I have a column of which autosum keeps a rolling count as the figures are entered and put them in a specific cell "G17"

What i need now is a macro that will take the figure in the cell "G17" and multiply it by 0.40 and put the answer in another cell for me "L20"
I would like to add figures in the column and watch autosum edit the figure in the first cell G17 "which it does at the moment" BUT also watch the figure multiplied by 0.40 in the other L20

I have had a look but could not find anything that would answer my question.
I though that asking people in the know would be a better option.

Thanks for the heads up,

Ian