Using spsList to set document metadata

Hi

A question regarding sharepoint integration, specifically updating meta-data pertaining to sharepoint documents using the spsList class / assembly.

Using the wizard generates a piece of code similar to

if (! (_spsList.SetDocumentMetaData(
_site,
_sharepointFolder,
_sharepointFile,
xml,
ref errorMessage)))

most of the arguments are self explanatory, and working fine

the piece of xml that is passed is

<Column Name="Client Name" Description="">Craig</Column>

This works fine

However, what I want to be able to do it to pass many values at once, rather than calling the web service many times. I tried passing a piece of xml in similar to this -

<Column Name="Client Name" Description="">Craig</Column>
<Column Name="Client Type" Description="">Private</Column>
<Column Name="Amount" Description="">1000</Column>

with no success. Although i didn't get an error, the meta-data was not updated at all.

There are a couple of reasons I would like to pass in all of the meta-data values at once. Firstly for performance - calling the web service once rather than many times (10 or more) will be much more effecient. Secondly, I have document versioning turned on in sharepoint. Each web service call produces a new version of the document, so I end up with 10+ versions when updating the meta-data - not efficient in terms of storage or searching for previous versions.

Could you tell me how I can update all of my meta-data with a single web-service call please.

Thanks