How do I call a function from an expression with current record as parameter?

How do I call a function from an expression with current record as parameter?

So I want to do this in an expression field:

thisapp.mynamespace.myfunction(currentrecord)

But, alas, how do I pass the current record?

Cheers and THANKS for any help!


And yes, I know "on update" and it doesn't fit my needs.