query 2 databases from one script

I've a script has many functions in it all of which hit databaseA . I've added a new function which is to get data from databaseB how can I go about this in one script when I try to connect to a database other than the one defined at the beginning of the script all the functions in the script break as if I am setting the wrong database at the top of the script. Any help would be greatly appreciated. Michael Roark