I have 4 check boxes and by default they are checked and depending on these check boxes i have to show a value some where else.

for ex:

suppose for first checkbox i say 1, second 2 ,third 3 and fourth 4
so initially i store this value in a string name dg="1,2,3,4"

if the user unchecks the second check box the value in my dg must be showing :
dg="1,3,4"

And again if the user checks the second chekbox , my dg must store the value :
dg="1,2,3,4"

How to achieve this? TX in advance