Create new property if doesn't exist

Hi,

I'd like to populate my container with some oher containers unless they exist.

So I've created:

Locals.Exists("TestCont.A",0)?
(
Locals.TestCont.NewSubProperty("A",PropValType_Container,False,"Container",0),
Locals.TestCont.A=Locals.B
):(True)

Container B contains two subproperties one string and second number.

However, I'm getting the error: Variable or property types do not match or are not compatible

How to do it correctly?

K.