Message box VBA - trigger to remain constant, need VBA to stop thereafter

Hey all

I have the following code which works upto as required. However when the user selects 'ok' i need the message box to discontinue.

The target cell will remain the same value. i.e. just a warning with no action required.

Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
If [A1].Value < 0 Then
MsgBox "Message here" & vbNewLine & vbNewLine & "Additional Message here", vbExclamation
End If
End Sub

Any help would be appreciated.