Shippment cost blocking from shpment level

Dear Friends,

I am using the shipment cost to do the payment. For that I am mentioning the Vendor name/code in the Shipment level and that vendor is reflecting in the Shipment cost level.

My query is that,

a) I would like to input the code of all vendors in the Shipment, but not always I will raise the Shipment cost against all of them.

b) For perticular Shipment, for particular vendor, I will not raise the payment invoice, and that I would like to block from shipment level, so that no one can raise the same.

c) I would like to assign this in each shipment level, not in the Master data level.

Authorization:

d) I need the authorization procedure to do the blocking.

e) not everyone can block or unblock on the above way.

My main objective is that, there are few shipment for which I would not like to raise the outgoing billing for that to the vendor.

Please try to guide me.

Rgds

Farhad