>The edit box is what I've tried, which gives me .selStart and .selLength, but I have to put up with ugly word wrapping.
>
>Modi file or modi comm gives me the option of turning off word wrap, but then I don't have easy access to positioning on the line - .selStart, .selLength. If I turn on the property 'show line/column position' for a modi comm window the row and column will show in the talk area at the bottom of the screen.

Try "Modify file whatever.txt range 45,55".