Invoice Total -SAPScript

Hi

Hope someone can help me as I've been struggling with this issue for a while.

I'm trying to sum the line totals on an invoice and then to display it as the total at the bottom of the page.

It's not getting an output.

This is the code I'm using:

/:PERFORM F_GET_PRICE IN PROGRAM Z000TOTT

/:USING &BSEG-BELNR&

/:CHANGING &TOT_PRICE&

/:ENDPERFORM

/&TOT_PRICE&

-

PROGRAM Z000TOTT.

FORM F_GET_PRICE TABLES IN_TAB STRUCTURE ITCSY

OUT_TAB STRUCTURE ITCSY.

TABLES:BSEG.

data: BEGIN OF IT occurs 1000,

WRBTR t