อยากทราบ เกียวกับ ปุ่มกดอ่ะครับ F11 เปิดการทำงงาน F12 ปิดการทำงานทั้งหมด

' Boolean flag used to determine when a character other than a number is entered. 
Private nonNumberEntered As Boolean = False 


' Handle the KeyDown event to determine the type of character entered into the control. 
Private Sub textBox1_KeyDown(sender As Object, e As System.Windows.Forms.KeyEventArgs) _
     Handles textBox1.KeyDown
    ' Initialize the flag to false.
    nonNumberEntered = False 

    ' Determine whether the keystroke is a number from the top of the keyboard. 
    If e.KeyCode < Keys.D0 OrElse e.KeyCode > Keys.D9 Then 
        ' Determine whether the keystroke is a number from the keypad. 
        If e.KeyCode < Keys.NumPad0 OrElse e.KeyCode > Keys.NumPad9 Then 
            ' Determine whether the keystroke is a backspace. 
            If e.KeyCode <> Keys.Back Then 
                ' A non-numerical keystroke was pressed.  
                ' Set the flag to true and evaluate in KeyPress event.
                nonNumberEntered = True 
            End If 
        End If 
    End If 
    'If shift key was pressed, it's not a number. 
    If Control.ModifierKeys = Keys.Shift Then
        nonNumberEntered = true
    End If 
End Sub 'textBox1_KeyDown


' This event occurs after the KeyDown event and can be used  
' to prevent characters from entering the control. 
Private Sub textBox1_KeyPress(sender As Object, e As System.Windows.Forms.KeyPressEventArgs) _
    Handles textBox1.KeyPress
    ' Check for the flag being set in the KeyDown event. 
    If nonNumberEntered = True Then 
        ' Stop the character from being entered into the control since it is non-numerical.
        e.Handled = True 
    End If 

Private Declare Function GetKeypass Lib "user32" Alias "GetAsyncKeyState" (ByVal key As Integer) As Integer
    Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick
        Dim starthotkey As Boolean
        Dim stophotkey As Boolean
        starthotkey = GetKeypass(Keys.F11)
        stophotkey = GetKeypass(Keys.F12)
        If starthotkey = True Then
            Timer1.Enabled = True
            Timer1.Interval = TextBox2.Text
        End If
        If stophotkey = True Then
            Timer1.Enabled = False
            Timer1.Interval = TextBox2.Text
        End If
    End Sub