i have an input form in which 6 rows of data intern give a sub total. what i would like to do is have a running / grand total automatically.

p2 =20
z2 =18 Grand total would read = 38
ac2 = 1 Grand total would read = 39
ad2 = 4 Grand total would read = 43
aj2 = 3 Grand total would read = 46
az = 2
Grand total = 48

can any one suggest a solution