The construction interest is modeled on the Dev-Interest Calc tab (show that tab by setting F43 on the Summary tab to ‘Show’). Interest is calculated as the Construction Interest Rate (Sources and Uses C15) divided by 12 (to arrive at a monthly interest rate) times the construction loan balance in each month (row 21) plus any accrued interest. This calculation is a circular reference, hence the ‘Set Construction Loan Amount’ macro on the Sources and Uses tab which iterates the calculation to arrive at an interest reserve and total construction loan amount.