"if i don't declare the function CreateArray(), as a reentrant function, then the array of 510 bytes, which, i tried to create inside the CreateArray() function, gets loacted at different memory area in the external RAM and not in the VIRTUAL STACK SEGMENT."

Why is that a problem?
That's the way it's supposed to work!

The only reason to mess about with the "VIRTUAL STACK SEGMENT" [1] is if you really need your function to be reentrant.

Do you actually need your fucntion to be reentrant?

[1] or whatever else a particular implementation may choose to call it