I feel really dumb asking this, but 1) I've never had to do it before, and 2)
I really did try it myself using Help!

I want to define a function I can call on a spreadsheet that'll take a cell
range (columns across a row) as input, and then step through the range of
cells in the function doing various things to the individual cells, then
return the result into the cell where the function is called.

In the spreadsheet (say, row 20) I'd expect to have a cell with, say,
"=DBA(J20:T20)" and the function (DBA) would take the 11 cells and loop
through them doing some math; to keep it simple, assume adding them up (I
KNOW there is a function to do that!) and returning the value.

In another row the same function would process the cells from that row.

I'm missing a fundamental concept, e.g., referencing the cell range in the
function and stepping through it. I am really not this dumb!

Can anyone provide a sample as a starter?