shift + up arrow.
Set your general broadcast channel to one window (turn off always type here). Name it "general sales" or whatever lets you remember. Do your spiel in that chat BOX.. go back to talking in your "normal" chat box (to your boxes? maybe lucky enough to have guildies?) Every 10, 15, 30 min, whatever your flavor is, pop cursor over, Shift + up, enter, will re-broadcast.
Now if your looking for the people who are selling 24/7 365 every 11 min, there are ways to do that (i dont know how), and I dont think your going to find that info here. Can always send a /t to bot sellars, when they check in a week, they might let you in on the secret