Executing Store Procedure

 
I have the following code. User clicks on a button, then textbox with
calendar icon is displayed, calendar appears when icon is clicked, user
selects date, date is populated in the textbox field.  The value in the
textbox field is passed to a stored procedure.  How can I check if the
sp call was successful and what can I do to add a message to the user.
 Also, is the control flow appropriate or should I change it?
 Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
   
 TextBox1.Visible = True
        ImageButton1.Visible = True
 
        If Calendar1.Visible = True Then
        ElseIf TextBox1.Text <> "" Then
 
            ' Create connection
            Dim conn As Data.SqlClient.SqlConnection = New Data.SqlClient.SqlConnection(SQLSTRING.ConnectionString)
            conn.Open()
            ' Create command
            Dim cmd As Data.SqlClient.SqlCommand = New Data.SqlClient.SqlCommand()
            cmd.Connection = conn
            cmd.CommandType = Data.CommandType.StoredProcedure
            cmd.CommandText = "sp"
            cmd.Parameters.Add("@date", Data.SqlDbType.DateTime)
            cmd.Parameters("@date").Value = Convert.ToDateTime(TextBox1.Text)
            cmd.ExecuteNonQuery()
            conn.Close()
        Else
            Response.Write("You must select a date.")
 
        End If