I added breakpoint and checked it out. When i use DEL key  to delete
the contents  of the cell, the value of Target.Address will be
$C$168:$E$168.
Same time  if i use backspace  to delete  the contents, the value of
Target.Address is $C$168. and i think this is where the problem is.
I am still not able to find the solution and working with it.