MS SQL - Loop through x number of record columns based on a user parameter

Hi,

I am migrating an old Crystal Report to an alternative Dashboard application.
My crystal report (which works very well, shame I have to migrate) reads from a table of monthly stock sales history.

e.g.

STOCK CODE   MONTH1UNITS   MONTH2UNITS   MONTH3UNITS   MONTH4UNITS   MONTH6UNITS   MONTH7UNITS
ABC123            100                         87                          69                          93                          108                        111
ETC
ETC

My Crystal Report had a parameter to prompt the user for number of months to report on.
A calculated field in the report registered all 60 of the month columns into an array and then looped through the correct number of months based on the user parameter for number of months to aggregate for each stock record in the report.
This solution was simple, elegant and worked very well.

I don't have the facility of arrays in the alternative Dashboard app.
Can anyone suggest an alternative way of achieving similar through SQL in Stored Procedure?  I'm struggling...

Hope i've explained clearly enough?

Thanks in anticipation...