generate list of Position wise student name

hi dear i am creating a list that generate a top 10 student name, i am create code Like this:

local stringvar message:={LIST_DPT_Exam_Marks_Sem_1;1.St_ID};

(
if({LIST_DPT_Exam_Marks_Sem_1;1.GPA}<3.00) Then
{LIST_DPT_Exam_Marks_Sem_1;1.St_ID}
);

but it generate  list but it create gap between list 

please tell me how to generate it 

Thanks 

Samiullah