Crystal Report COnnection in VB.NET(2005)

I want to change the connectiong string to open Crystal Report(built-in) in VB.NET(2005).

VB Code:

Dim rpt As New rptInvoice
rpt.SetDatabaseLogon(userid,password,servername,databasename)
CrystalViewer1.ReportSource=rpt
CrystalViewer1.Show()

But the ServerName does not change. It still alert a message to input username and password(disable the field servername).

Please help me.