NPV

Have you checked the Financial Functions ( NPV is one ), Use the find function wizard and then Finanacial,

Roy

The simplest way is to divide your annual interest rate by 4 (4 quarters)
=npv(x/4,-capital, q1_income,q2_income,q3_income...)

A more precise interest rate calculation if compounding quarterly is (1+x)^(1/4)-1
ie if x=10% would be (1+.1)^(1/4)-1=.024114 instead of x/4=.025