Make a cell blink by it's entered time plus 2 hours

If I have a time value in cell A1 as 00:00, how can I use VBA to make the cell blink when the current time is 2 hours greater than A1, and stop when cell has no value or empty? Here is the homework I've done. I've never really messed with VBA so forgive my ignorance. Maybe I can use a variation of this, editing the "If Range("A1") = "1" in the code?

MODULE

Option Explicit 
Public RunWhen As Double 

Sub StartBlink() 
    If Range("A1").Interior.ColorIndex = 3 Then 
        Range("A1").Interior.ColorIndex = 6 
    Else 
        Range("A1").Interior.ColorIndex = 3 
    End If 
    RunWhen = Now + TimeSerial(0, 0, 1) 
    Application.OnTime RunWhen, "StartBlink", , True 
End Sub 

Sub StopBlink() 
    Range("A1").Interior.ColorIndex = xlAutomatic 
    Application.OnTime RunWhen, "StartBlink", , False 
End Sub

CODE

Option Explicit 
Public CellCheck As Boolean 

Private Sub Worksheet_Change(ByVal Target As Excel.Range) 

     'Change the IF statement and cell range to what you need
    If Range("A1") = "1" And CellCheck = False Then 
        Call StartBlink 
        CellCheck = True 
    ElseIf Range("A1") <> "1" And CellCheck = True Then 
        Call StopBlink 
        CellCheck = False 
    End If 

End Sub