Help with Sum distinct

[#1]

Hi,

I have the following working exp:

sum({$ <Type -= {'FLEET'}>} if(TD_Commision = [Commission Number],1))

the problem is, there could be repeated data where for example  TD_Commission can occur 20 times, and I am strugling how to add distinct funtion to it.

any ideas 

thanks in advance

[ToniKautto · Accepted solution]

What happens if you just add DISTINCT in the expression?

sum(DISTINCT {$ <Type -= {'FLEET'}>} if(TD_Commision = [Commission Number],1))