iTunes Smart Playlists: Songs not played in the last 6 hours

I'm hosting a barbecue on Saturday that is likely to go on well into the night, so I have compiled a playlist of approximately 10 hours of music. I want to make sure that if I need to stop the playback and start it again, I don't want to hear the same tracks already played recently. In conclusion, I'd like to create a Smart Playlist that will only show songs that haven't been played in the last 6 hours. Unfortunately, the "Last Played not in the last" shortest option is 1 day. I considered the "Limit to XX items selected by least recently played" option, however that will mean the music will be skewed towards music I haven't listened to for the longest, which is not what I want, because that ends up grouping lots of a similar artist together and it won't feel very random. I tried entering a fraction for number of days, but it doesn't allow that. Does anyone have any ideas on how I could get this to work?