Finding rows where one column is the same but a second is different

[HorsePop]

After the roaring success of my last question here I thought I'd try again.

Basically what I want to do is find rows where

a) One column is repeated in other rows
AND
b) Another column is different to other rows where the first column is the same.

A) is easy enough using countif.

What I now want to do is b) but the difficult part is getting it to only look in rows where the column I am looking in for a) is the same and not the whole sheet.

The value in column B isn't going to be unique to that row so I can't just look down the whole column.
How can I delimit it to just cells where col A is a duplicate?

Here's some sample data.

It's the WhatIWantToDo column I want to fill in. Note that it should show 2 for the apples because there's two lines with 20kg on so one of them shouldn't be counted.
Note also that the weights are repeated throughout the col but it's only looking at rows where col A is the same so it is spotting them as unique.

Fruit	Weight	WhatIWantToDo
Apples	10kg	2
Apples	20kg	2
Apples	20kg	2
Oranges	10kg	1
Oranges	10kg	1
Bananas	10kg	3
Bananas	20kg	3
Bananas	30kg	3

[hamjam]

Hello there
Just to confirm, what I understand is that you want to determine the number of unique records, that are unique through the combination of cols A and B. This answer should be written to all rows that contain the first element of the unique value (i.e. derived from column A)

One of the non-VBA solutions would be:
there is a cool function called remove duplicates which is found in the data menu
select both columns (as you need both values to form unique set) and remove the duplicates
this will reduce your data
you can then copy column A data, perhaps to a new sheet
repeat remove duplicates function which should leave you with just the unique fruit, lets call this unique fruit data
enter the formula

=COUNTIF(your list of fruit,cell of 1st unique fruit data)

copy that formula down to cover all elements of your unique fruit data, ensuring that the list of fruit is static > meaning you keep that range

Regards