How to count checked checkboxes in QTP

Set a =Description.Create
a("html tag").value="INPUT"
a("micclass").value="WebCheckBox"
a("checked").value=0

Set b = Browser("Colony Rater 3.0").Page("Colony Rater 3.0").childobjects(a)
'If b = "ON" Then
c=b.count
'End IF
msgbox c