You have to make a 2nd page in the event (the barrel in this case).
Just go into Event-Edit-mode (Doubleclicking the Event) and on top of the window are 4 buttons (New Page, Copy Page, Paste Page and Delete Page).
Klick on the New Page button and set the Start Condition, that Switch "Herb" is ON (on the left of the window, check the first line and choose the Switch "Herb").

Leave the Main Window blank or type a text message, such as "Nothing here anymore" or something like that.

Up until now, only the second page will be used for this event, since the Switch Herb is on...and so (I think you got it already )