ReportText is a custom step property, not a static step property. Thus there is not a "hard coded" function to access it. Here is some code that should work:
// error checking omitted
void foo(CAObjHandle step)
{
char * reportText = NULL;
VBOOL exists;
TS_PropertyExists(step, NULL, "Step.Result.ReportText", 0, &exists);
if (exists)
{
TS_PropertyGetValString(step, NULL, "Result.ReportText", 0, &reportText);
// use reportText here
}
CA_FreeMemory(reportText);
}