Production forecast


I do want to register an production forecast for an BOM-item in AX2009.

My item deduction is periodic, almost everything goes in June and November but my production takes place all year around.

I have tried to use sales forecast but get problem when my inventory balance for sales item add up and I do not get any planned manufacturing orders.

Any suggestion to solve this. E.g. I want sales forecast without include on hand inventory for sales item but include on hand for my purchased items.