VBA to insert a timestamp when a value changes

Hi Excel experts,

I would highly appreciate if someone could help me figure out a VBA to insert a date and time stamp in a cell based on the value change from another cell.

Please note this is not a request to ask when a data entry action has been performed to make the change.

It is a request regarding when selecting a certain value from a data validation dropdown list to change the value in another cell based on IF function, so a date and time stamp can automatically populate to mark the change.

Example from the attached sheet:

3 different men named A, B and C.

A weighs 180 lbs., B weighs 200 lbs., and C weighs 210 lbs.

By default, Cell B3's value is always A. So Cell C3's value is always 180.

Changing the value in Cell B3 from A to B, can ONLY be done by picking "B" from a dropdown list in Cell B3.

This is to say, NO MANUAL DATA ENTERING/ CHANGING can be done to make this value change from A to B.

In this case, how would I be able use VBA to insert a date and time stamp in Cell D3, when every time a new value in Cell B3 has been SELECTED/ PICKED (NOT ENTERED) from the dropdown list?

For instance, currently Cell B3 is "A". I picked "B" in Cell B3's dropdown list on 08/12/22, 12:00:00pm.

What would be a VBA to mark this stamp automatically in Cell D3?

Again, your help is GREATLY appreciated!

Thank you so much!!

Please see example files thank you.

The formula in C3 is "=IF(B3="C",210,IF(B3="B",200,IF(B3="A",180)))".

In B3 there is a dropdown list of "A", "B", "C".

Just wanted to have a timestamp in D3, whenever I pick A or B or C in Cell B3 then Cell C3 changes to 180, 200 and 210.

The timestamp should mark the time when it changes from 180 to 200, 200 to 210 etc.

Thank you so much!!!!