Restart stopwatch from previous time

Hi, I am using a stopwatch script that allows me to start, stop and reset in the active cell. The only problem I have is that when I go back to a previous cell with the time already inserted, it resets back to 00:00. I would like to continue the time from the previously inserted time. For example if I want to start from 00:00 I would first have to enter it into the cell and then press reset or if 10:00 is inserted it will reset to 10:00 and when start is pressed it will continue to count up from 10:00. Another way to say it is that I would like the stopwatch to start from whatever time is already inserted in the cell. Any help would be much appreciated.

Here is the code that I am using:

Dim StopTimer           As Boolean
Dim SchdTime            As Date
Dim Etime               As Date
Const OneSec            As Date = 1 / 86400#

Private Sub ResetBtn_Click()
    StopTimer = True
    Etime = 0
    [ActiveCell].Value = "00:00:00"
End Sub

Private Sub StartBtn_Click()
   StopTimer = False
   SchdTime = Now()
   [ActiveCell].Value = Format(Etime, "hh:mm:ss")
   Application.OnTime SchdTime + OneSec, "Foglio1.NextTick"
End Sub

Private Sub StopBtn_Click()
    StopTimer = True
    Beep
End Sub

Sub NextTick()
   If StopTimer Then
      'Don't reschedule update
   Else
      [ActiveCell].Value = Format(Etime, "hh:mm:ss")
      SchdTime = SchdTime + OneSec
      Application.OnTime SchdTime, "Foglio1.NextTick"
      Etime = Etime + OneSec
   End If
End Sub

Hi Leith, just a little follow up question: Can it restart using the text from the formula bar instead of from the cell?

Many thanks