Smartform Server Level Validation

HI

I have a smartform which acts as an electronic version of a specific document. The k2 process of which the smartform belongs to has an XML Field which uses the structure defined by a schema used to represent the fields on the hard-copy form.

I need the following:

1) How do I explicitly force the smartform to update the XML Field in the k2 process without using the K2 Update Activity button??
2) How do I retrieve the XML field data in the K2 Process for validation (i.e. call webservice to validate xml data)??