Ok so like I said that worked brilliantly but now I want to add an if to the expression.
This is my script,
if(UNIT.GRADEFIX = '' , '', num(avg(UNIT.M_MILEAGE / 1000) + Avg(UNIT.AGEMONTHS) + Avg(UNIT.GRADEFIX*10) + Avg(UNIT.CAPCLEAN_ORIG /1000))) as Buyer.GCT_Score
group by %_BNO;
It's again saying invalid expression?