BEX calculation of Average Month Unit

Hi,

Could you help me on identifying a solution for our report computation for average of month units? The need is to get the YTD units and divide it by the month of the date parameter. So its Average month units = YTD unit / month

For example:

the date parameter selected is for May 15, 2014 (05/15/2014)

YTD unit is 7,000

The average month unit is calculated as 7000 divide by 5 = 1,400 units.

How could we get the month based on the date selection so that we can use it for the calculation of the average month unit?

Hope you can help.

Thank you.