How do I apply a style to a docVariable?

The scenario is that there is an input form from which the user selects various options. Each option is represented by a docVariable in the active document. If the option is selected, the docVariable value is equal to a certain string. If it is not selected, the docVariable value is equal to " ". ("" Gives me Errors unfortunately).

In a few instances, a style needs to be applied if the option is selected. How do I get at it to apply the style?