Input Current Date Into A Field By Clicking Checkbox

Does anyone know how to automatically enter the current date into a specified field by simply clicking on a check box. I imagine the IIf function would work when entered into 'Control Source' but I also need the check box to be linked to the underlying table.
i.e. I tick the 'Paid' checkbox and the current date is automatically entered into the 'Date Sold' field. I also need the -1 generated by clicking on the checkbox to be stored in the table.

Any suggestions would be appreciated, although I am no good with code, so if you could post an example or an easier way to do it I would be most grateful