Start Timer When Cell Is Selected?

I am trying to write a simple macro that would start a timer (in hh:mm:ss format) when the cell is selected. In other words, if I have the following:

Row Col B Col C
1 00:00:00 (form btn)
2 00:00:00 (form btn)
3 00:00:00 (form btn)

I would like to select B1 to start a timer and C1 (button) to stop the timer for that row.

I was given code from another IT guy but the problem with this code is that I have to write multiple macros by just switching out the cell number (in this example = [C4] )

I would like to have the macro use the selected cell as input parameter in the line that reads Set count = [C4].

Dim CD As Date
Sub RunTime()
CD = Now + TimeValue("00:00:01")
Application.OnTime CD, "Counter"
End Sub

[code].....