Public Class clsUser
    Public IsLoggedIn As Boolean = False
    Public Name As String = "View only"
    Public Password As String = ""
    Public Group As Integer = 0
    Public LogoutTime As Integer = 0
    Public Comment As String = ""
    Public Function Login(ByVal Group As Integer) As Boolean
        Try
            Dim f As New frmLogin
            If f.ShowDialog = DialogResult.OK Then
                Return True
            Else
                Return False
            End If
        Catch ex As Exception
            mdlFunctions.Exception(ex)
            Return False
        End Try
    End Function
End Class
 
 
Public Class frmLogin
 
    Private Sub btnOK_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles btnOK.Click
        Try
...
            With frmStart.User 'das ist die Instanz. Eigentlich sollte hier 
            ' stehen: clsUser
                .IsLoggedIn = True
                .Name = row.Item("User").ToString
                .Password = row.Item("Password").ToString
                .Group = CType(row.Item("Group"), Integer)
                .LogoutTime = CType(row.Item("LogoutTime"), Integer)
                .Comment = row.Item("Comment").ToString
            End With
            Me.DialogResult = Windows.Forms.DialogResult.OK
            Me.Close()
        Catch ex As Exception
            mdlFunctions.Exception(ex)
            Me.Close()
        End Try
    End Sub
End Class