Restrict column to editing

Hi All
Just wanted to know how I can restrict the edit option for a blank column once I entered something.

As an example in the attached excel
1) Under request ID if I put numeric data then I should not have access to edit the same field for the 2nd time
2) Once I update something in the "Request" column the "Date" and "Time" column should get the update automatically and capture the entry date and time
If anyone suggests me some code it will be very helpful.



Regards
Arindam

Attachment 737342


attached file