sum field in table

hallow

i have table with emp miss for month and i wont to add another line with sum of miss days for month how i can do that ?

kostl         month1      month2    month3      month4     month5     month6
1000-10	532	456	503	453	522	500
1000-11	23	20	21	19	22	20

for this table ccmissdays i wont to add line with bold (sum)

kostl         month1      month2    month3      month4     month5     month6
1000-10	532	456	503	453	522	500
1000-11	23	20	21	19	22	20
            <b>555          476           524            472          544           520</b>

Best regards