JEFF wrote...
....
I'm trying to marry the cashflows for year 0-10, with a perpetuity for the
beyond 10.... Sounds like I'm missing something.
....

Use Solver. With 0-10 cashflows in a range named CF, a constant
perpetuity cashflow named P, and a cell named i holding the interest
rate, enter the formula

=NPV(i,CF)+P/i/(1+i)^10

Then use Solver to set this formula to zero by varying i.