Manipulating Save Button Based On Readonly Attribute

I am trying to use the following code to make the save button invisible in
the asp form when the checkbox is either on or the session variable has a
particular value.

THE CODE IS AS FOLLOWS:

<%If ( cbool(l_IsChecked) = "FALSE" ) or (session("sess_FiscalFirst") <>
"Y") then%>
<input type="submit" value="Save" name="btn_Save">

<%End If%>

In the above, my logic is if the value of the checkbox is not true or the
value of the session variable is not Y then only show the SAVE button.

However this is not happening. I find that when the second part or the first
part is not there, the logic goes fine i.e. the logic holds with only the
first condition or the second condition itself but not with the or syntax.
Not sure why.