Need help with dividing column with column total

[#1]

I have a column that is totals up how many items in a classification

=NUM(count(DISTINCT(ItemNumber)))

That works great, but I want to divide the row total for the item classification with the column total for the items numbers.

For example

Item Class     Number of items Percentage of Items

                         50                         100%

Pink                   10                         20%

Blue                   20                         40%

Green               20                           40%

I need the forumla for the percentage of items

[#2 · Accepted solution]

percentage

count(Number of items)/cOUNT(TOTAL Number of items )