Return total amount values based on multiple criteria

Hi, can someone help me on what formula to use in cell C4:BB6 under MASTERFILE on my attached file. I want to modify it in such a way that the the formula is based on the date headers and the rows that shows "Total" on the sheets.

I do not want to simply reference a cell since the row numbers may change from time to time, and so instead I want my formula to be able to reflect the total amount for each week ending based on the dates and the row that has a row header of "Totals".

Can you also help me on what conditional format formula should I use in sheet FORECAST - CONSTR. What I want to happen is for those rows to be highlighted in blue fill if the vlookup does not return a value for start date. And to highlight in blue with red font those cells in which the vlookup return no value and thus the dates were instead base on the forecasted days of return.

Appreciate you help! Thank you so much!