Syntax for expressions in NF field controls

Versions: Forms 1.2.0.0 and Workflow 2.3.7.0

Hi,

I'm trying to work out what the syntax for controlling a form field state (such as Enabled) with an expression is.

I started off with Enabled on a field set to Expression with a simple function-

fn-IsMemberOfGroup(Knowledge Managers)

and that worked fine. However when I extended that into what (I believe) is a valid Javascript-style expression-

fn-IsMemberOfGroup(Knowledge Managers) && (Item Status != "Pending")

it stopped working (the field is always disabled).

The equivalent excel-style single-function expression (more verbose and difficult to understand), doesn't work either-

fn-And(fn-IsMemberOfGroup(Knowledge Managers), fn-Not(fn-Equals(Item Status, "Pending")))

with the same always-disabled result. Each of the pieces inside the fn-And() works on its own, but the larger AND expression doesn't.

Can anyone give me any pointers on-

1. What the correct syntax for nontrivial expressions in forms are?
2. How to debug these? Is there an error log or some way of "watching" the evaluation of these rules at runtime?

Any help much appreciated.

Regards: colin_e