Calculate average on the fly and also check if the 2 values are different before setting the default average

I have a table which can have 4 x 4 =16 combinations of value .

I need to figure out "avg" for each and also determine if they are "different" and then decide the "default avg".

The default avg rule is to check if the values of 2015 and 2014 are different and then populate it to the lower value 

i.e 1.5 then 2

2.5 then 3

e.g if 2015 =3 and 2014 =4 then different would be 1, avg would be 3.5 and then default avg would be set to 4(lower value)

f 2015 =1 and 2014 =2 then different would be 1, avg would be 1.5 and then default avg would be set to 2 (lower value)

 Should this calculation be done on the table or on the SSRS ?

Does SSRS experts recommend this operation with an expression ?