Code:
Dim obj_check
Dim allcheckboxes
Set obj_check=Description.Create
obj_Check("html tag").value="INPUT"
obj_Check("type").value="checkbox"
Set allcheckboxes=Browser("micclass:=Browser").Page("micclass:=Page").ChildObjects(obj_check)
a= allcheckboxes.count()
For i = 0 to 17
allcheckboxes(i).Set "ON"
Next
here 17 is the value of the count of check boxes in my project. I think it will solve ur problem