Combining Indirect with Match

What exactly do you want to sum?

Your 2 MATCH formulas are going to return the column number where the value in B250 is found in row 5.

For example if the value in B250 was found in column 5 you would be summing row 5.

I'm trying to sum the entire column.

The entire column where you find the value from B250 in row 5?

You could try something like this.

=SUM(INDEX(A:Z,,MATCH(B250,5:5,0)))

You can create the SUM range with an OFFSET function:

=SUM(OFFSET($A$5,0,MATCH($B$250,$5:$5,0)-1,1048571,1))

Syntax of OFFSET is:

=OFFSET(Reference Point, Row Offset, Column Offset, Height, Width)

Reference Point - a known starting point, in this case you know your headings are in row 5 so the starting point can be A5
Row Offset - the headers are in row 5 so set to zero so no row offset
Column Offset - this is the unknown factor so is determined by matching B250 in row 5; the offset will then offset by that number from column A so needs reducing by 1 to get correct column.
Height - the number of rows to include in the sum, I have set to the absolute maximum (max rows of 1048576 less 5 as you are starting on row 5)
Width - just summing one column so set to 1.

Perfect thank you very much.

You're welcome!
Thanks for the feedback.