[GRASSLIST:3456] Sites & v.surf.idw in G57 - attr in Postgres

[Funkmeister]

Hello, This is possibly a dumb question, but I can't figure out what to 
do based on docs, and other postings.

I am trying to use v.surf.idw to create a DEM in G57. My sites/vector 
file was imported from ESRI coverages using v.in.ogr. The elevation 
values are stored in a Postgres table. How can I get v.surf.idw to see 
those elevations? I get errors like:

decimal field 1 not present in sites file

I doesn't matter what I enter for the field, keep getting a similar 
error.

So what do I need to do? Create a temporary vector file with my 
elevations stored within? How do I do that?

Thanks
Craig