I’m not shure if I understand you correct, but I think you could achieve this with the Frank Buss Formula module
but please don’t ask me what the right formula for it is 
or Nysthi should have a module for this
I’m not shure if I understand you correct, but I think you could achieve this with the Frank Buss Formula module
but please don’t ask me what the right formula for it is
or Nysthi should have a module for this