I am making a invoice out of a spreadhseet using functions and the such.

I want to make the invoice kind of a "template" i guess you could say with
all the functions in there, just need to enter the values. And lets say I
don't have any items on lines 2-8, so I want the total amount to be 0, or
hidden.
Example: In Cell I-15, the function is "=F15*G15". In F-15 the value is 2,
G-15 the value is 65, because I did 2 hours at $65 per hour. In I-15 it comes
up and says $130.00. That's great. But what I wanted to know is if say I want
to enter the rest of the formulas down the invoice (I have 10 lines preset).
But IF I dont put anything in rows 16-25, then instead of $0.00 showing up in
Cells I-16 - I-25, it won't show anything. Is this possible? I can provide
the spreadhseet if you need better clarification. Thanks!