After update of an option

Hi,

I have a very basic form used for entering registrations and the locations of the vehicles.

To chose the locations a combo box is used with a drop down list. When the location is chosen it is stored in a field.

I also have a long text box on the same form. What I would like to do is if a user changes a location of any registration the change from and to and the date of change is put in the notes box so there is a history of it.

Is there some piece of code that could be written to say something like "Location changed from *current* to *new selection of location* on *date*. Then if it is changed again the next change is saved on a new line in the notes box? I've attached a screen shot of the form if it helps.

Thanks,
Lewis