Transformation routine - ABAP Code required

Hello ALL,

I am new to ABAP programming.

I have requirement where I need to calculate the field ZATTN based on the sales quantity and Invoice date.

The formula required for ZATTN is as follows

ZATTN = (sales qty * no.of days in Invoice Month) / Invoice date (DD)

For example -

Sales Qty = 100 and Invoice date = 2009.06.05

ZATTN = (100* 30) / 5

Here

value 30 is based on the month from Invoice date (2009.06.05), for month 06, no of days = 30.

value 5 is based on the day from Invoice date(2009.06.05), for day DD = 05

Please provide logic for the above.

thanks,

Pra