=Sum(A1:A7)

Do you want to turn the fill color red or the font color red? If the
former, try conditional formatting (Format/Conditional Formatting). If the
latter, try a custom number format (Format/Cells/Custom)

[Red][<1](0%);0%


"j5b9721" wrote:

a1 has 10%
a2 has 30%
a3 has 10%
a4 has 20%
a5 has 5%
a6 has 15%
a7 has 10%

a8 needs to be ONLY "100%" total the above percentages or default to red in
color if below 100%