How to use an "expected delivery" date as deal value instead of expected sales date?

How to use an "expected delivery" date as deal value instead of expected sales date?

We are magazine publishers, selling advertising space. We recognise only the published date, rather than the date of sale in all our sales and accounting functions. The sale date is irrelevant to us for all practical purposes.

I would like to put the deals module into place, but we need to have a way of forecasting our potentials by published date (month) than sale date.

For example: A deal may be for say a half page in ABC edition of the magazine in May, June, July 2018 at say £100 per month.

So our variables are
- Edition
- Month/Year
- Size
- Price

I need to know how to set this up so I end up with forecast reports showing me the potential revenue for each month by edition and size.

I have tried with the field tools available in the Reports section but am running up against the problem of the Month/Year and edition being a multi pick list, so they are not available to me in the reports.

Any assistance would be appreciated thanks in advance