I declare parameters in this way

static PRM_Name theFileName(“file”, “Particle Bin File”);
static PRM_Default theFileDefault(0, “$HIP/in.$F4.bin”);

PRM_Template templateList = {
PRM_Template(PRM_STRING, 1, &theFileName, &theFileDefault),
PRM_Template()
};

How should I evaluate them in cookMySop function, to make expression evaluated? I tried channels, expressions - in best case I get $F4 substituted to “0001” with this call

UT_String PATH()
{
UT_String str = “”;
evalString(str,0,0,0);
return str;
}

But parameter editor shows me correct values :? :? :?

where may I find reference or similar sample?

Thank you!