Calculate Prod. Order Starting Date NAV 2013

MiSta78

Dear all,
we are using the planning worksheet to plan our production orders based on forecast. The suggested prod. orders in the worksheet have an unrealistically early starting date and therefore we order our components for these orders far too early. Alltogether everything is setup quite correctly, but some of the routing lines we want to exclude completely from the calculation of the starting. Is there any standard functionality to achieve this:
"Consider routing line (or work center) in calculation of standard cost, but exclude this routing line (or work center)" from the starting date calculation?
If not, any workarounds? Of course I set up the concurrent capacity for this routing line to i.e. 100000, but I do not consider this to be a good solution...
Thanks a lot
MiSta