Here is an example of how I connect to my database using variables:
OLEDB CONNECT TO [Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=$(vDBName);Data Source=$(vDBServer);Use Procedure for Prepare=1;Auto Translate=True;Packet Size=4096;Workstation ID=$(vWorkstation);Use Encryption for Data=False;Tag with column collation when possible=False];
Note that vDBName, vDBServer, and vWorkstation are all variables that I had populated earlier in my load script.