Maybe something like this would help.

Put this in V4 and copy down:
=$T$1*AVERAGE(OFFSET(B4,0,$U$2,1,$U$1))+
$T$2*AVERAGE(OFFSET(B4,0,0,1,$U$2))

I started in row 4 because row 3 has the headings.

If all the cells in an average are empty, there will be a #DIV/0
error. If this is a possibility with your data, add a check for this
case.

Modify as needed.