Excel percentages using if/then?

I have an excel form for a sales peice which all I want to have tallied is all the dollars that I put are 80% sure or above, if they are 79% or below, than it won't add it to the total column. The two columns are side by side and run down the page. So, I am thinking I need an "if/then" statement where if the percentage is 8-% or higher add the number to the total in the column to the right? Can somone please help?!?