Les
In an unused cell type =A5+A22+A100 and hit the <ENTER> key.
If those cells have numbers, you will get an answer.
OR you could use =SUM(A5+A22+a100) which ignores cells that are not numbers.
i.e. A5 = 123, A22 = 123, A100 = "les"
The SUM function would return 246
=A5+A22+A100 would throw an error.
Gord Dibben Excel MVP