How to fetch objective name from line_object_id in objective line scoring fast formula

We wanted to put some condition around objective name (scoring is different for objectives start with WPR and HPR) but I am  unable to do so as I am getting error when submitting objetive.

Standard formula :

/* Defaults for optional inputs and database items */

DEFAULT FOR performance IS 0

DEFAULT FOR weighting   IS 0

/* Declare formula inputs */

INPUTS ARE  performance(number)

          ,weighting(number)

          ,line_object_id(number)

          ,appraisal_id(number)

           ,appr_template_id(number)

          ,appr_system_type(text)

           ,appr_type(text)

/* Main body of formula */

          line_score = performance * weighting

/* Return the line score */

RETURN line_score

and I wanted to put condition in main body like :