Search and replace in a string

Hi,

my problem: is there any posibility to search and replace inside a string?
Search an replace the whole string is no problem, but i want to search and
replace only the part of a string:
e.g. the name of a street:
Hauptstr. 13
Gartenstr. 47
Wiesenstr. 48

i want to replace the "str." with "strasse":

Hauptstrasse 13
Gartenstrasse 47
Wiesenstrasse 48

Thanx
Rainer