Relative output folders in Droplet/Batch

I'd like to create a Droplet or Batch from an Action in CS and have the resulting images saved to a folder that is relative to the original images folder i.e. ../Output. I can't work out how to do this - it only seems possible to set an output folder explicitly.

You can specify the folder to save in in the batch action dialog box (override action save as command)

But you have to do it everytime you run a batch of your action.

You may be able to do it with scripting, check out the PS scripting forum for more (and better) help