Is there a string to inet function that can be used in order by ?

I have a table of strings categorized by string type and unique id

e.g.

stringTypes table (sType, sDescription)
0 vanilla
1 ip address
2 mail address

stringValues table (sId, sType, sValue)
1 0 foobar
2 2 123 Main Street
3 1 123.123.123.123
3 1 123.13.123.123

I want to select ip address type strings and order them by ip address. However I can not find a function that returns an inet given a string.

e.g.

select sValue from stringValues A, stringTypes B
where A.sType = B.sType and B.sType = 1
order by [**** function that converts string to INET ****] (A.sValue);

TIA

Richard DeVenezia