math functions inside views 3
It really all depends on where $total_order is defined/declared etc.  You might be able to use the http://drupal.org/project/computed_field module to do the math and just rewrite the field with the text "spend [field] euros more...." to do it, or, if that doesn't work, or adds too much complexity, just create a views template for the field that does the math in php there and displays the field.