A way to type-on from the RIGHT?

OK, I think one or the other of the expressions experts here can probably answer this quite quickly.

I want to modify a simple "Type-On" (or more precisely "Word Processor") effect so that:

rather than the text being stationary while the selector moves along to reveal the text, we keep the 'insertion point' stationary and have the text flow away (to the left) -- rather like typing your text in a Word Processor when the paragraph is right-aligned.

Some of AE CS3's presets like "Insertion Point" and "Stack Left Stack Right" seem to be going in the right direction for this but they are only approximations, offsetting based on percentage of range, and an arbitrary position value. Not enough to make the effect look right, especially if you have a flashing "insertion point/cursor" at the selector, as in the built-in (left-aligned) "Word Processor" effect.

Is this actually possible?

I have the impression from other posts I've read here that because it seems neither possible to 1. get the *actual* position of the selector at any point of time, nor 2. return the actual height or width of the text layer, let alone individual lines, that there may be no possible method for offsetting position precisely.

Thanks for any comments,

LMN