How do I handle textbox events for input?

Private Sub Calculate_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Calculate.Click
        Dim NewTextBox As Boolean = True
        For Each ctrl As Control In Me.Controls
            If TypeOf ctrl Is TextBox Then
                If CType(ctrl, TextBox).Text = "" Then
                    NewTextBox = False
                End If
            End If
        Next
        If NewTextBox Then
            Dim newtext = New TextBox
            newtext.Location = New Point(300, 300)
            newtext.Size = New Size(150, 150)
            newtext.Text = "ehsan"
            Me.Controls.Add(newtext)
        End If
    End Sub