Using Item Cross-Reference in creating Purchase order

Hi -

Items > Cross-Reference

EX :

Type : Old Codes

item:  X     ===>    Value:  Y

After Defining Items and linked it with Values [Old code for example] i am able to use this value [Y] in creating sales order for example

Can i use it also in creating purchase order ? any setup required ?

Can i use this value in any other standard function ?

Thanks