PSPICE - Text string problem

Hi all,

What I need to is define a text parameter, and compare it with another string.

below is my spice code: 

.SUBCKT XXX 1 2
+ TEXT: Material_Name = "AL"

R 1 2 {IF(Material_Name=="AL", 100, 200)}

but the pspice compiler said:

**** EXPANSION OF SUBCIRCUIT X_R1 ****

ERROR(ORPSIM-15166): Bad expression
 Material_Name is used as a PARAM here, but used as TEXT elsewhere.

ERROR(ORPSIM-15081): Can't add param <Material_Name>.
X_R1.R N00056 0 {IF(Material_Name=="AL", 100, 200)}
----------------$
ERROR(ORPSIM-16318): Missing or invalid expression

my question is, what is the correct syntax for comparing two string values...

thank in advance