Do you want to dimension a hole to a datum axis? Try this.
I originally posted this for use in a discussion, but it also seems to be a good fit for the How to video challenge.
Its easy to choose an axis as a reference for a dimension, but you must then choose a second reference. If you want the dimension to the axis to maintain a straight line from the hole center to the axis, then it appears that the second reference cannot be on a plane that is parallel or perpindicular to one of the planes that the axis is contrained to. I know that is a big sentence, and I hope the video and some experimenting will help it make sense.
I have not studied all possibilities for choosing references for holes, I am only commenting on the technique seen in the video.