Monthly fees in Forecasts?

Hello community!

Since I'm pretty sure, this can't be achieved by Admin-methods, I'm posting this in the developer space.

So, here is our situation: We are working opportunities-only in Sugar, which we have related to the product catalog module - so each product catalog entry works as a template for x opportunities. This works totally fine for us.

Our products are mainly features of and additions to our online platform(s) and those are often charged monthly. We have those "monthly fees" as a field in the opportunities.

We haven't been working with the Forecasts-module yet, as I always was under the impression that it is not possible to change the "source fields" for the calculations done there, so no chance to take those monthly fees into account for the forecast. But then again, we can't be the only company with monthly fees for their products, so I don't want to give the feature up for us entirely yet 

So here are my questions:

  • Is it possible to modify the "source" fields used by the Forecasts-module?
  • Could the Forecasts-module calculate with monthly fees? If yes, how?
  • Do you know best practices or how others are doing it?

Thanks in advance for replies!