Smartform debugging issue

Hi Experts,

I have sales invoice sf in which I have to add one more tax i.e tcs (1%).

In the text of one of the cells in the main area it shows:

&itab-total-vat1&

&itab-total-et1&

&itab-total-cst1&

In its program lines, i have written code like total1 = total + total_vat1 + total_et1 + total_cst1. If I debug this, the values are not coming and in the output its coming. I want the total of all this and calculate 1%. How to do it?