I have several groupings of rows and I wish to sort these groupings based on
the cell value in one cell in each grouping. How can this be done?

For example... rows 1 & 2 are grouped and rows 3 & 4 are grouped, if I wish
to sort these grouped rows by the cell value in C2 (= 6) in the first group
and cell value C4 (= 7) in the second group without changing the groupings,
how would I do this? The values in column C are equations, i.e., C1 = A1 + B1

A B C
1 2 2 4
2 3 8 11
3 1 2 3
4 3 4 7