I'm working on a spread sheet and I am using the following Formula:
=SUM(B5*(1+B4/12)-B3)

I want to use the autofiller to repeat the formula on the following rows
ONLY replacing B5 with the next sequential number, but keeping B4 and B3 as
constants as I drag the auto filler down. for instance:

B6 =SUM(B5*(1+B4/12)-B3)
B7 =SUM(B6*(1+B4/12)-B3)
B8 =SUM(B7*(1+B4/12)-B3)
B9 =SUM(B8*(1+B4/12)-B3)

When I highlight the cell and drag the auto filler down, I get :
B7 =SUM(B6*(1+B5/12)-B4)

I tried manually entering the formulas listed above on B6 through B9 and
highlighting all 4 and then dragging the auto filler down, to allow excel to
recognize the pattern that only the first cell reference was changing and not
the other two, but it continues to change all three. Is there any way to
lock B4 and B3 in the above formulas so only the first one changes?