Function can not use the 'NEW' variable as a direct parameter inside trigger function?

Hi,

Why a function can not pass the 'NEW' variable as a direct parameter ?
When I use myFunction(NEW) inside a trigger function an error appears :

pq_driver: [PGRES_FATAL_ERROR]ERROR: function myFunction(MyTableStruct)
does not exist
LINE 1: ...myFunction(NEW)...
^
HINT: No function matches the given name and argument types. You might
need to add explicit type casts.

I have to use trick by using a temporary variable to run the code :

theVariable MyTableStruct;
theVariable = NEW ;
myFunction(theVariable) ;

Thanks