Is this what you were looking for? The attached example uses the Superstore Sales sample data with two custom calculations - one to effectively assign each batch of orders to a custom bin (using an IF/THEN statement), the second a table calculation to calculate how many customers fell into the bin.
I believe the table calc in the sample needs to use compute by Cell instead of Table-Across to get the number of customers.
Nice catch, Patrick! I was still learning table calcs then. Actually, I'm still learning table calcs, only I know a bit more now. The Compute Using Cell works, however it is drawing 5100 marks by creating stacked bars, on per Customer. I've added an optimized view that only draws one mark per bar, that uses a Compute Using of Customer.