Weekly cost of sale array formula

Hi All,

I am building a worksheet that calculates the cost of a salesforce by week. In row 30 of the attached, I am looking to populate the total spend on TSMs (salespeople) up to, and including that week. The dates that are listed in row 28 are the beginning of the week.

I think I understand how to do this on a line, by line basis, but I'm really struggling with the array formula (I think it is an array that would do this best?)

A few points to note:

1) Each TSM dedicates a different amount of their time to the specific product in question, meaning they have different annual cost allocations (Sumproduct would work for this part)
2) TSMs start on different days, meaning each has a different proportion of their annual salary recorded as cost to-date (individually, this can be solved using a combination of COUNTA to recognize the amount of TSMs, multiplied by 365, divided by the number of days they should have recorded determined by an IF function)

Thanks,
B