Here are a couple suggestions depending on your playstyle. I'm leaning towards using a single Acrobatics roll, but I'll run these options by my players if/when they attempt it and see which they'd prefer.
If you really want to simulate all the steps of this action, you'll need multiple rolls.
After some input in comments and reviewing a few videos to better understand how wall running actually works, I think my initial suggestion was backwards.
A wall run starts with a jump up to the height at which the person is going to run, followed by a series of steps along the wall and a final jump off the wall.
Jumping up to a certain height is Athletics.
The steps on the wall must be precisely angled so that they don't push the person away from the wall, and even more precisely angled to actually help the person stay up and move forward.
Precise foot movements are Acrobatics.
Then there is a final push-off from the wall, which is essentially a long jump.
Long jumps are athletics.
The mechanics for high jumps and long jumps are well understood, and don't require further discussion here.
So, I think the question would be: how far does the character get to run along the wall?
Here, the rules get vague and leave it up to you to pick a DC... somehow. I figure it would make sense to model it along the long jump rules, but using Acrobatics instead of Athletics.
The world long jump record is 29 ft 41⁄4 in, or about 6 squares. This is from a running start. That would require an Athletics check of 30. The world record for a wall run is about 12 feet. Wall running is not an Olympic event like the long jump, so let's optimistically assume that if it were, and countries around the world were spending absurd time and money on finding/creating the best wall runner, someone could get 15 feet, i.e. 3 squares.
So, I'll say you need an acrobatics check of 30 to get three squares along the wall, which means divide the result by 10.
So, if your Athletics and Acrobatics are similar, you could actually get further jumping. If however your Acrobatics is much higher, like my player's character's is, then wall running might be a better option.
High jump Athletics check for height, Acrobatics check divided by 10 for distance along the wall, long jump Athletics check for distance jumped after leaving the wall.
Not everybody wants to roll multiple times for a single action, and doing that habitually can slow the game down.
As Wesley Obenshain has pointed out, the steps on the wall don't really help much. It's mostly just a long jump. So, you could just assume they make it up onto and off of the wall fine, and have them roll a long jump to see how far they get along the wall. If you need to determine how high up the wall they got, use the Distance Cleared Vertically section of the long jump rules in the Rules Compendium, and figure they're that high up.
However, since the whole point of this is that, in the player's mind, this is an acrobatic action rather than an athletic action, I think it would be perfectly reasonable to allow them to roll Acrobatics instead of Athletics.