DTS - How to pass a variable into an "Execute SQL task"

Experts,

I am writing a DTS package that users will run from the command line.
I want them to be able to pass in a parameter at the cmd line that I can pass into a stored procedure via an Execute SQL task.
I have got my global variable setup to trap the incoming parameter and I can pass it in from the cmd line OK.  The problem is that I cant find a way of passing it into the prcoedure call.
Ultimately what I'm looking for is to be able to do this in the Execute SQL node :-
exec <procedure name> parameter1 = <DTS global variable>

How can I best do this?

Thanks in advance
Meowsh