create procedure MYPROC 
returns(mesto varchar(??? /*сколько у тебя там длина может быть*/ ))
as
declare variable vBETW varchar(???);
declare variable vCONER varchar(???);
declare variable vSTREETONE_STREETNAME varchar(???);
declare variable vDOM1 varchar(???);
declare variable vKORP1 varchar(???);
declare variable vSTREETTOW_STREETNAME varchar(???);
declare variable vDOM2 varchar(???);
declare variable vKORP2 varchar(???);
begin
for SELECT NEWBUILDLIST.BETW, NEWBUILDLIST.CONER,
           STREETONE.STREETNAME, NEWBUILDLIST.DOM1, NEWBUILDLIST.KORP1,
           STREETTOW.STREETNAME, NEWBUILDLIST.DOM2, NEWBUILDLIST.KORP2 
      FROM NEWBUILDLIST 
           INNER JOIN STREET STREETONE ON (NEWBUILDLIST.STREET1 = STREET.STREET_ID) 
           INNER JOIN STREET STREETTOW ON (NEWBUILDLIST.STREET2 = STREET.STREET_ID) 
      into :vBETW, :vCONER,
           :vSTREETONE_STREETNAME, :vDOM1, :vKORP1,
           :vSTREETTOW_STREETNAME, :vDOM2, :vKORP2 
   do begin
     mesto='';
     if (vBETW is not null) then mesto=mesto||vBetw;
     if (vCONER is not null) then mesto=mesto||vCONER;
     if (:vSTREETONE_STREETNAME is not null) 
       then mesto=mesto||' '||vSTREETONE_STREETNAME;
     if (vDOM1 is not null) then mesto=mesto||', '||vDOM1;
     if (vKORP1 is not null) then mesto=mesto||' / '||vKORP1;
     if (:vSTREETTOW_STREETNAME is not null) 
       then mesto=mesto||' и '||vSTREETTOW_STREETNAME;
     if (vDOM2 is not null) then mesto=mesto||', '||vDOM2;
     if (vKORP2 is not null) then mesto=mesto||' / '||vKORP2;
     suspend;
   end
end;