[REBOL] Declaring Arrays

[rebol . phb]

Is it possible to use a variable to declare the size of an array ?

my-array: array [3]

When using ....
j: 3
my-array array[j]

or
j: 3
my-array: array[:j]

I get the error

** User Error: Integer size required.
** Where: make error! "Integer size required"


Cheers Phil