Sum values in multiple columns with same index number

[vikrampnz]

Hello

I have made a cash flow sheet to show Apartment Sales Inflow per month. (Please see attached sheet)

I have created various Rules in sheet "Gaps" showing when proportionate payment will be received for each construction stage of a particular apartment, by putting Month number under each stage in the table.

Second Sheet has Unit number wise costing details for each Apartment and the stagewise cost break up for each construction stage.

Third Sheet, which is my cash Flow sheet shows the Money inflow for each month based on when each apartment was sold and which construction stages are complete for respective apartments.

Now this sheet works perfectly well for me for Apartments which are sold at begining of the construction cycle.

My problem is, when I assume a sale of an Apartment at a later date when my first 5 construction stages are completed, I expect that the Sum of those completed stages should reflect in CashFlow sheet (See Rule number KR0319 in sheet GAPS, where first five stages are shown complete in Month 1) under the Sale Month in CashFlow sheet, which will be the First payment Month for that particular apartment.

Can someone please help ! Would really appreciate it.

Thanks