Lookup and Sum given time-based criteria

[dukebluedevil]

I have a lookup that Index/Match should perform nicely with the exceptions of a couple of wrinkles. I am consolidating income statement line items from a single store (unit) template. As I open new stores across periods, the I/S line items layer into the model. The line items change on a monthly basis. I need to layer in multiple opening across different periods AND sum in a single formula so that by the end of the model projection period, the line items in the consolidated I/S include all 100 stores figures. The template income statement for a single store uses generic headings for each period such as Month 1, Month 2, Month 3 etc for 120 months whereas the consolidated income statement uses actual dates across the forecast period. How can I accomplish the consolidation? match will not work because the template period headings (the generic ones) do not "match" the dated period headings of the consolidated periods. Also, how do I write the lookup so that the consolidated I/S incorporates and Sums the individual stores values at the appropriate point in time (once the store is scheduled to open)? Lastly, I have a tab for the market development forecast which is a series of 1s and 0s that represent the dated period in which a single store is projected to open. Multiple stores/units open simultaneously across the projection period.