Barring a switch (which is lame, just for that), and making a Condition- If Old Guy Gave you 10 gold, you can also do it by variable. Set the variable to 1 after a single time, then make a condition - OldManGift = 1 at the top of the page, with an else. put the gift inside the else, and add the variable Set Equal to 1 at the end of the else, and voila! You have a single page event. You can even string several conversations on a single page, like so.
Condition - OldMan is 2
-(Whatever you want)
Else
Condition - OldMan is 1
-(Etc)
-Variable OldMan, Set 2
Else
Condition - OldMan is 0
-(More crap)
-Variable OldMan, Set 1