Monitor Purchase Order flow with 2 vendors

Hello,

My client is buying a product which is manufactured by 2 vendors.

No component is provided to the vendors, only product specifications.

The first vendor creates a semi-finished, then sends it to a second one and the second one delivers

the finished product to my client.

What would be your suggestions to monitor each step in MM if there are no intermediate goods receipt at my client'site ?

Thanks a lot for your help

Ordibrio