Hi GB,
Because no one has yet to respond, I feel I should "start the ball rolling"...
I didn't respond earlier because I don't have the version of Lotus you're referring to - Release 9.
I, like SO MANY others, have stuck with Release 5. My understanding is that in many others cases, others have actually "reverted back" to Release 5. I won't go into the reasoning here because it would be too long a response, and if you look, you can probably find an earlier posting of mine related to this same subject.
Back to your question... Specifically, I don't know the answer in "LotusScript" (which is the "terrible mistake" made by Lotus/IBM).
I can provide the answer in the language used in Release 5. I'm not certain, but I think the later versions of Lotus do maintain compatibility with this programming code. By the way, it doesn't have a name - first "blunder" by Lotus Corp. I've opted to call it "SNAP" - for Super Natural Application Programming.
Finally, the answer (in SNAP code) is...
{END}{RIGHT}, {END}{LEFT}, {END}{UP}, {END}{DOWN}
The above, however, will NOT "anchor" as per your description of what you need.
I don't have Lotus 123 at work, so I can't double-check, but I'm fairly sure that the following is what will work to "anchor" and select a range...
{SELECT-RANGE-RELATIVE columns,rows}
where you replace columns and rows with numbers.
I believe there's also a third option (argument) that allows for the selection to extend across worksheets. It would come after "rows".
I hope this helps.
It'll be interesting to see if anyone out there will provide the code in LotusScript, and to see how it compares.
I hope this helps.

Please advise as to how you make out.
Regards, ...Dale Watson dwatson@bsi.gov.mb.ca