Multiple IIF query

[snowball]

I am trying to do a calculation in access to look at machine efficiency, my
problem is i have a number of possible process steps to look at and calculate
I currently have the following:

Total quantity products = Qty
Target Quantity Per hour = TQty
No of panels produced = panels produced
Actual time machine was running = RunT
Process operation = Operation

My process steps (i.e. (operation) are:
DIP
Rad
Combi

Each of these has a predefined "Target Quantity per hour" in a process table
which i have linked to my query.

My efficiency calculation should be something like ([Qty]/[TQty for the
relevent operation]*[RunT] so depending on the operation selected the Tqty
should reflect its std Target quantity per hour.

Any ideas how to approach this?

 

[snowball]

Should read Total quantity produced = Qty