custom check box issue

hi, 

I have a custom check box written for my grid as i have nested loop , i a unable to implement the appian default selection check boxes. 

here is the code, 

a!richTextIcon(
icon: "square-o",
link: a!dynamicLink(
saveInto: {
a!save({local!selectedIndex},fv!index),

a!save(local!selectedProcedure, append(local!selectedProcedure,fv!item))
}
),
linkStyle: "STANDALONE",
showWhen: tointeger(local!selectedIndex) <> fv!index,
color: "SECONDARY",
size: "MEDIUM"
),
a!richTextIcon(
icon: "check-square-o-alt",
link: a!dynamicLink(
saveInto: {
a!save(local!selectedIndex,null),
a!save(local!selectedProcedure, difference(local!selectedProcedure,fv!item)),
}
linkStyle: "STANDALONE",
showWhen: tointeger(local!selectedIndex) = fv!index,
color:"SECONDARY",
size: "MEDIUM"
),

This code actually , appends the index in the local!selectionprocedure  but when i unselect it , it actually removes the last item in the local!selectedProcedure but not the actual index unselected. Any leads will help.