Excel 2003

I have a YTD actual productivity number and need to forecast what the
productivity would need to be over each of the next 7 months to achieve a 15%
full year increase. The result would need to include the Headcount
reduction/increase for each month.

Productivity = (transaction/headcount)*(YTD Sales Days/monthly Sales Days)

I have each month's transactions, YTD Sales days and montly Sales Days.

Is this possible?