Change a cell formula based on a pulldown selection that changes formula argument

Hello!

I have a series of data cells for reference at the top of a sheet, and they have pulldown lists for 3 different units. I want to create a formula to calculate a value that references this data cell, but the formula changes depending on the units selected (in this case $/kgal, $/gal, and $/m3; in my case, data cell is G4, list cell is H4 and cell reference =$N$5:$P$5 ($/kgal, $/gal, $/m3)
When G4=$/kGal, then fx = G11*I11*K11*M11
When G4=$/gal, then fx = G11*I11*K11*(M11*1000)
When G4=$/m3, then fx = G11*I11*K11*(M11*0.264172)

How can I do this? I am first timer, so I will try to attach a sample sheet for reference. Thanks for help.

Russ

Thanks Ace_XL! Works perfectly!

Very Kind Regards,

Russ