Does anyone know how to compare dates in VBSCript in the format mm/dd/yyyy?

In VB just simply declare the variables as
dim a as date
dim b as date
but what do you do in VBSCript?

the following code will generate the text "a is greater than b" - obviously not true
<%
dim a,b
a= "05/23/1999"
b= "01/23/2000"

if a > b then
response.write "a is greater than b"
elseif a = b then
response.write "a is equal to b"
else
response.write "a is less than b"
end if
%>

any help is appreciated!

B