How do I quickly edit a number I just dialed

My God i'm going nuts.. I travel right on the edge of a long distance zone so when someone calls me and I return their call I get "this is a long distance call" and you need to put a (1) infront of the number you are trying to call.

Now the only way I can see to do that is to save the nubmer and try and edit it. not that I want to save every single junk number I get every day.

Is there any quick way to edit a number you just tried to dial??

thanks frustrated.