It looks like this is on the same level as what I want to do, but I can't get
the formula to work. It gives me an error message saying "A value used in the
formula is of the wrong data type". I don't understand as all of the data
used in the formula is of the "Number" type.

"Glenn" wrote:

JLewis wrote:
I have a spreadsheet with current inventory on hand and the sales for each
month from the last year. I want to figure how many months our inventory on
hand will last based on the last years sales. For instance, WidgetA has 100
on hand and Mar, Apr, May, Jun & Jul sales were 5,10,15,40,60, respectively.
I know that we have 4.5 months supply, but I have to manually figure this
calculation. I have more than 400 items. This takes a long time to figure, is
there any way to automate the figuring of the months supply?

Look at this:

http://tinyurl.com/bndrvj

If you are having trouble making it work, put your worksheet on www.savefile.com
and I will see if I can help.