Trying To Get The Right Registry Key Through Sql Script To Change Listen Port

Hi,

I want the change the SQL listen port of a named 2005 sql instance.

Is there a way I can run an sql query against the named instance which
gives me back which registry setting I need to use.

so MSSQL.1 MSSQL.2 or MSSQL.3

Or is there another way I can set the listenport through script or
vbscript for only a specific named instance so if there are other sql
server instances running they don't get affected.

Thanks Bob