Need a formula to have check marks control adding up cells in different column

Trying to use numbers for a quick & dirty budget. I'd like a column of check boxes to control whether or not a different column's cells are totaled up.

For example, C column is full of prices. D column is all check marks. I'd like the footer cell of D column to total up ONLY the cells in C column that have a checked box next to them in D column.

I'm not the best with formulas yet, and this one is stumping me. Thanks!