Reasonable To Assemble FullName W/ A UDF

I break somone's name in a table in fields as First, Last, Middle,
Suffix.

Is it reasonable to use a UDF to create the full name as a string if I
need it, by passing it the First, Last, Middle, & Suffix fields?

Is this really slow to do? It's just sometimes I want to do a GroupBy
Query and I want to include the person's name in the Select of the
query and I don't know if the group by would work if I returned each
column seperately.

Any opinions on this?

Thanks.