Variance of one month over the same month of the previous year?

[#1]

Hello,

I feel like the answer is obvious but I cannot seem to figure ot how to create an expression for my cross table to add a column that would divide the sum of sales for that month by the sum of sales for the same month in the previous year...?

Any help is appreciated!

[#2]

Can you give us some data to work with?  Sample data set or QVW

I am sure someone will be able to help you with this!

[#3]

Honestly not really, I can make some data up for you though? The data set I am using is confidential.

I just threw these numbers together, but it should suffice, I would simply need the sum of all the sales in Jan 2012 to be divided by the sum of all the sales for Jan 2011 and so forth for each month, but have the result show as a variance %.

(IE if Jan 2011 sales were $100 and Jan 2012 sales were $120 the new column would display +20%)

This is my first time posting here so please bear with me if I am not following normal protocol for asking questions.

Sales	Year	Month
34563	2012	Jan
56377	2012	Feb
23451	2012	Jan
72743	2012	Feb
51346	2012	Jan
16123	2012	Feb
34563	2011	Jan
13546	2011	Feb
12341	2011	Jan
16123	2011	Feb
54264	2011	Jan
44515	2011	Feb