How to place reservation on a sales order line with visible demand flag set to 'No'

Hi;

I created a sales order line with 'visible demand flag' set to  NO

with that setup, I'm not able to see the sales order line during ATP calculation and that's OK

but I need to place a reservation on the sales order in other to reserve the quantity requested

can some one tell me the best way to do that?

for the moment I have tried the reservation using the schedule ship date on the sales order line

but this is not working because, the line is now available for ATP inquiry

thanks a lot for any reply

michele onga