Sharepoint- Inserting in a list subfolder

How can I insert a list item in a folder within a list, using list web services (UpdateListItem).

The breadcrumb of the folder would be something like this. [My site] > [My list] > [My sub folder]

I have tried with a CAML like this:

 <Batch PreCalc="TRUE"
 OnError="Continue"
 RootFolder="/Lists/MyList/MySubFolder">
 <Method ID="1" Cmd="New">
       <Field Name="Title">Gent</Field>
       <Field Name="PostalCode">9000</Field>
       <Field Name="TelephoneZone">09</Field>   
</Method> </Batch>

But unsuccessfully.

I am getting as response: Invalid URL value.
**If I remove the RootFolder attribute it works fine, but the item gets inserted outside the folder.

From stackoverflow

• Have you tried inserting the item into the list, then making a second call to update the metadata and stick it in the right folder?

  AlejandroR : Inserting the item in the list no problem. How to update it later so it goes into a given folder I don't know how to do.

• If you're able to deploy code to the server i'd roll my own web service that does the job. That way you get access to the entire object model.

• Problem solved.

  The "RootFolderAttribute" should not be RootFolder="/Lists/MyList/MySubFolder" but "/sites/MySite/Lists/MyList/MySubfolder"

  Could solved it thanks to a tool named u2u CAML Query Builder.

  Jason Watts : Yes, MySites is on a seperate site collection, so the /sites/ wildcard inclusion is required. CAML Query Builder is a great tool btw and has saved my hide many a time!