>So what is the straight-forward way to get my data in to the updatable cursor?

Here is how to do it (from Ed Pikman)
---------------------------------------------------------------------
Any read-only cursor can be converted to read-write one programmatically and subsequently its structure can be changed:
Select MyField From MyTable Into Cursor tmpReadonly NOFILTER
cDbf=dbf()
Select 0
Use (cDbf) AGAIN ALIAS tmpReadWrite
Use In tmpReadonly
Alter Table tmpReadWrite Add Column MyNewField C(10)
----------------------------------------------------------------------

Note that you can change the cursor, but the updates are not sent back to the original cursor.