Looks like you are pretty close, this is what I have used to do something similiar
With ie.document
Set elems = .getelementsbytagname("input")
For Each e In elems
If (e.getattribute("className") = "saveComment") Then
e.Click
Exit For
End If
Next e
End With
You will probably just have to change the if statement.
I also notice that your code refers to .Name = "Prefill"
but your html snippet refers to .value = "Prefill"