I'm not sure which function(s) to use to accomplish this.
Column A has a checkbox that indicates this line is included
Column B has a checkbox that indicates a 50% discount of an amount
Column C has the amount
Say I have 3 lines of data
I want to add the amounts in column 3 if the 1st box is checked but if the 2nd box is checked, I only want 50% of the amount added.
Recommendations?

First recommendation would be to post an example workbook so we can see exactly what you're working with.