Convert Excel SUM IF formula array to VBA code

I need to pare down the number of calculations on the worksheet because it is slow. I'm trying to convert the following formula to a VBA code.

{=SUM(IF(I:I>=AI3,IF(I:I<AI4,1,0),0))}

in my code:
col1 = "I"
col8 = "AI"
i = 3
the current cell = AL3
col11 = "AL"

Does anyone know how this could be represented in VBA to fill in the value for that cell instead of putting the equation in? I'm a bit lost on this one.

Thanks!