Vehicle Sign Out Log - Auto Save, Auto Date & Time

I am a REAL novice at this and am asking for your kind assistance in getting this going.
I've created a vehicle sign out log (as shown below).
1. Column "B" is where student will select their names (simple drop down menu);
2. Column "C" is where the student will enter their driver's license info.;
3. Column "D" is where the student will enter their destination;
4. Column "E", I was able to copy a code from this forum where the date is automatically entered triggered by Column "B";
4a. Can Column F be programmed to auto enter time, too?
5. Column "A" is where the student will enter the vehicle # which is provided by the guard-on-duty once columns B, C, D, E and F are filled.
This is where my hiccups are and would like the spreadsheet to work as follows:

During vehicle check-out:
1. Auto Save the workbook when closing (without the need for the user to save) once Columns A - E are filled;
2. Auto Lock the filled cells (A - E) before closing to prevent anyone from deleting entered information; Keep Columns G & H unlocked for vehicle turn-in.

During vehicle turn-in:
1. The user/student enters the date and time in Columns G & H (hopefully we can do an auto time entry also when "G" is filled). Then,
2. Auto Lock the completed columns to prevent tampering.

I hope I'm making sense!

Thank you in advance.

Claudee