The Taysiders' 2-1 victory over the Light Blues was the first at Dens Park since August 1992.
The win took Dundee into sixth place in the Ladbrokes Premiership and Hartley wants to remain there at the split.
Ahead of the trip to Motherwell on Saturday, he said: "Last week's result was terrific; that has now gone.
"We all enjoyed last week, the players, staff, supporters, it was a good feeling for us.
"It had been a long time in beating Rangers but what we did stress to the players is that it can't be a one-off.
"We have to maintain that form and the high standards we set and hopefully we can have that from now until the end of the season."
Despite moving into sixth, Dundee are 10 points behind fifth-place St Johnstone, with the four sides below them all within three points of their tally.
And Hartley is eager for his side to keep their noses in front in the race for a top-half finish.
"We have managed to get in (the top six)," he added
"We feel there is probably only one space left and three are four or five teams trying to get in.
"We have given ourselves an opportunity but we have to continue what we did last week.
"Our whole focus is on a tough away fixture at Motherwell, who have good players.
"They have had a couple of bad results but we know that they are a real threat.
"So we have to take last week's performance into this week's game."
Source : PA