How to defince PO category wise approval limits

Hi,

As a business requirements we want to have PO category wise approval limits and approval.

Case :-

Each department preparing four types of PO

1) Stock PO

2) Non stock PO for marketing (items field will be kept empty and only description is provided in the PO lines)

3) Non Stock PO for fixed assets (same as 2 and asset clearing account is slected in PO distribution charge account)

4) Non Stock PO for others (same as 2 other then marketing and fixed assets)

In on approval hierarchy the approval limit is different for all above 4 PO categories.

Please advice how to apply this business requirements.