Adding separate data to an existing Pivot Table? - Looking for suggestions or how to?

[ez08mba]

I want to add separate data (a monthly forecast goal) to this pivot from a different spreadsheet of data so I can display it as a separate "forecast" column next to each stacked column month. The data in this pivot is obviously the sum of a chart of data. However, the forecast data is already summed so it would count as "1" instead of (for example) "100" which is the goal for June and "110" for July etc.

That's my first issue.

My second is the user needs to be able to alter the forecast.

Any guidance, suggestions, ideas? Feel free to ask any questions that will help me explain better the goal if necessary.

Thanks!