Concatenation using variables

I need to have a result column in my report be a concatenation of text and conditionally, 1 or 2 addtional text 'values'.

"Donor+xxxx" - in every row
conditionally, if donor # from table 1 matches a donor # from table 2, I need to concatenate "+yyy"
Further, if the State in another table = a certain value, additional concatenate "+zzz'

Both the yyy & zzz are optional

End results could be any of:
Donor+xxxx
Donor+xxxx+yyy
Donor+xxxx+zzz
Donor+xxxx+yyy+zzz

yyy and zzz are not present in any table, just text values to concatenate.

I've been playing with using variables and concatenations and Related, but no success.