I am trying to sum a large group of non-contiguous cells. Such as
+sum(A1,A4,A23) etc...

Is there a limit to the number of "parts" to the formula?

I am getting an error, but it is non-descript and only highlights a cell
reference in the formula. I deleted the highlighted cell reference, but I got
the same error again, this time with the next cell reference highlighted.

Is there another way to accomplish this?

This is part of a master file that contains 20 years worth of data and I
need to avoid any major revision to it.

Thanks