It would appear that I seek a solution in the wrong place...
My users would like to have four specific fields on a form to entirely highlight the existing contents when selected during edit.

By typing, the original contents would be over written.

Highlighting does not occur for either of the following code:
In Form Init/Refresh during edit mode
- thisform.cLENGTH.SelLength=7
- thisform.cLENGTH.SelStart= 2
Nor, In Got Focus of cLENGTH object
- this.cLENGTH. (etc...)

What are these Properties good for?