Change Annotation Anchor without Moving Its Location?

I want to change the anchor position of an annotation without moving it from its current location. In other words, I want to do the equivalent of executing the following two lines sequentially without having the annotation shift its position on the graph:

TextBox/C/N=text0/F=0/A=MC "Some Text"
TextBox/C/N=text0/A=LT

Can this be done without having first to parse the recreation information for the tag to find its current location and recalculating in terms of the new anchor location?

(Update)

I see that, when I change the anchor location using the dialog box, the x and y offsets automatically adjust to keep the annotation in the same place. I want that same affect to be possible when changing the anchor location via a program.