I believe that Kodak publishes some times for D-76 1:3. I would look at how these times relate to the 1:1 times, and apply the same ratio to D-23 when you try it out at 1:3. For instance, if the times for D-76 at 1:3 are 1.7x the 1:1 times, try D-23 1:3 at 1.7x the 1:1 times and see what happens. I made up the 1.7x factor.
Make sure you shoot a composition that has a fixed and a known luminance range, so you can accurately judge the development. You cannot know for sure if you are developing too much or too little if you do not know what the normally developed negative should be. You know this only by knowing how things in the shot measured with your light meter.
I wouldn't use it diluted that much for pushing, and you should also realize that you will get more graininess.
I've never developed Tri-X in diluted D-23 – just 1:1. I have not used the developer for that long, or done exact testing with it. I did use it 1:7 for stand development of FP4 a few times, with so-so results (too flat, but printable). If you do the math, 1:7 times would be very long, but 1:3 times are more reasonable. I would start at 1:3 and see if you like it...but remember that time is money, and developer is cheap. If this is just an attempt to save some money, I would find other ways to save in the darkroom aside from diluting your developer.