Re: What is the syntax of a variable, to use it in an expression ?
The syntax to use a variable is $(), so:
When you use a variable in this way the content of the variable is effectively copied and pasted into the location where the $() appears.
Note that behaviour is different if your variable content begins with an equals symbol, as in this case the variable code is evaluated outside of the object where it is used and the result is returned.
$(=some(expression)) effectively calculates the expression outside of the context where the variable is used also.
Hope that makes sense?
Instinctively, I have never put a period in any of my variable names, but I see no reason why it shouldn't work. If it doesn't maybe try just VarPV.