I'm assuming you want some form of popup help, not how to create a document/manual or an html type of help file.
One way is a table of the explanation field and possibly fields for form name and control name. If you're already using double click event for any of these, could use a combination of mouse event (e.g. mouse up or down) and the shift value. That is, if shift or alt or ctlr or any combination of these keys are held down, you open up a little form that has what you need in the way of explaining, which comes from the help table. That is based on the form name and control that this is being run on.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.