Can I set a "redefinable" variable equal to a "define_dgn" variable in GEOPAK criteria?

If so, what is the syntax?

I'm trying to get something like this to work:

define_dgn "string1" \
    dgn = C:\string1.dgn \
  lvname =  string1

define_dgn "string2" \
    dgn = C:\string2.dgn \
  lvname =  string2

if x >0 then

_s_string = "string1"

else

_s_string = "string2"

Thanks.