Generate a unique time stamp per x instruction cycles? Is it possible?

I have been looking into some more challenging topics and this came up. Basically, I need a way to create a unique time stamp after a far smaller value than a second which seems to be Excels smallest unit. Any help is appreciated here.

Public Function TimeInUS() As String
     Dim x As Integer
     For x = 1 To 10
          Range("B" & x).Value = x & "_person."
          Range("A" & x).Value = z     'TIME STAMP HERE <-------------
     Next x
End Function

Where 'z' is a new value slightly greater than itself a few microseconds ago. I need a value based off the time since I may run this program today, export the information, and re-run the program tomorrow with new data. The timestamp is a way to keep track of entered values througout all time.

Maybe over kill doing it this way but any help is appreciated. Thank you.