Making a cell wording change dependant on multiple selections

Hi, I'm pretty novice on Excel VBA and have been trying to work out how to make a cell value change if certain drop down responses are selected, but to no joy. I'm hoping someone can push me in the right direction.

So I'm trying to return either Tier 0, Tier 1, Tier 2 or Tier 3 in tab 'Instructions & Glossary' cell E12

So in tab 'Generic Information' if a user selects the following it returns Tier 0;

C10 use existing
C12 >4 (numbered selection up to 20)
C13 Yes
C14 Yes
C22 Yes
B31 AD / Radius Server

or

If a user selects the following it returns Tier 1;

C12 >4 (numbered selection up to 20)
C13 Yes
C14 Yes
C22 Yes
B31 AD / Radius Server

or

If a user selects the following it returns Tier 2;

C10 use existing

or

If a user selects the following it returns Tier 3;

C10 anything other than use existing
C12 <4 (numbered selection up to 20)
C13 anything other than Yes
C14 anything other than Yes
C22 anything other than Yes
B31 anything other than AD / Radius Server