I think we need a bit more detail on exactly how you set this up.
Can you format a global field with a conditional value list? yes.
Can you select a value in global field 1 to control the values listed in the conditional value list on global field 2? Yes, if global field 1 is defined in the "parent" table and if that global field is specified in the relationship on which the conditional value list is based.
Can you list values stored in a global field in your value list? No, only indexed fields can serve as a value list's source of values.
Can you list values from a calculation field that refers to a global field? No, this calculation can only be an unstored, unindexed calculation and thus it can't serve as the value source for your list.