Select more value of variable in planning folder

hi gurus,

I'm using planning folder.

In planning folder there is a variable that contain many value, for example 0COSTCENTER that contain 10 singles values. (from 1 to 10)

User wants to select some values contained in variable.

For example 2 and 5, even if it is authorized on all the cost center contained in variable.

In this moment it selects one to the time.

how I can make to resolve this problem?

Thanks

Davide