Excel Time Request Assignment - VB Code/Macro

I need to automatically add date with time on a column once adjacet cell is filled out but once it is set it must remain and not be editable.

I found a really good VB script.... just that the cell can be errased and so does the time stamp.

I've attached the file I'm  Working ON... the Green Columns are the TIMESTAMPS while the yellow represents the fields of the names of assignation.

This site has the VB code I copied:
https://excel.tips.net/T003116_Recording_a_Data_Entry_Time.html

Problem is I don't know where to place column in question:
Column N Timestamp is dependent of  name entered on Column O.
Column Q Timestamp is dependent of name entered on Column P.

I believe I have most of it down

coding just isn't my skillset....
CONTROL-ITN-JG.xlsm