Help with excel formula please

Jason1985 

The reason I have 4 different columns is they relate to 4 different sales KPI’s. Hence why I am not sure it can be made any simpler, as each individual KPI has its own target set.

That is what wasn't made clear (or it's what I missed). I saw no reference to four different KPIs in the original post, only to four drop downs, with no reason given for them.  

I have created a possible way to do it, using VLOOKUP and a table for the percentages. HansVogelaar  has given you a different approach.

In this example of mine I just calculate what each drop-down evaluation would do (subtract from or add to that base bonus) and then do a single add of the results in cell L9. The key formula is this:

=$E$9*(VLOOKUP(F8,$F$1:$G$5,2,1))

The result looks like this:

If this is NOT what you want it to do, then, for the sake of being completely clear, can I ask you to clarify how you envision these four adjustments working together. Could you actually work through a complete example or two in plain English and math, but not in Excel. As if you were on a blackboard (or whiteboard--your choice) so that HansVogelaar and I can see how this algorithm plays out as we would if talking with you in person.

Include whatever base salary is involved as well, if that gets affected. I assume that the end result, that base bonus of 5% is applied to the base; that's why I ask. So I'm wondering, for example, if poor performance on each of the four KPIs can result in a reduction of base salary....and so forth.