you use outlook? email him on behalf of manager/director/ceo (so it looks like it came from their email...) informing him certain aspects of his behaviour in the office/performance has been brought to your attention, you are not happy and want a meeting first thing in the morning at a set time/location.
watch him squirm for rest of day, make odd comment, then next day laugh when he comes to office after time of set meeting...
you use outlook? email him on behalf of manager/director/ceo (so it looks like it came from their email...) informing him certain aspects of his behaviour in the office/performance has been brought to your attention, you are not happy and want a meeting first thing in the morning at a set time/location.
watch him squirm for rest of day, make odd comment, then next day laugh when he comes to office after time of set meeting...
repeat.