No there is not a way to do this with the @code in the template. The work around would be to create another field and name it xyz- your choice- and populate the field. That way you have 2 fields 1 caps 1 not. Make sense?
Being able to capitalise text fields on a template would be a highly beneficial feature to have. We use separate fields as you've described Karrie and it works okay but is not ideal. Being able to put something along the lines of ^UPPER^@Lastname onto a template - or be able to build it into a style tag (eg /Fverdana/C144 0 0/UPPER) and have it convert to uppercase would be a big time saver