Put the IP address of the machine where the Sql Server instance is installed in the connection string when you access the database. Example:
connectionString="Server=XXX.XXX.XXX.XXX\SQLExpress;AttachDbFilename=c:\asd\qwe\mydbfile.mdf;Database=dbname;Integrated Security=True;Connect Timeout=30;User Instance=True;Provider=SQLOLEDB;"
Where XXX.XXX.XXX.XXX is the IP Address