Base network profile on result of VRO Workflow

Currently based on the property hard coded in the build profile of VirtualMachine.Network0.ProfielName  the network and ip's get assigned in vRA.

However, now we have a requirement to base the network that the vm goes to on outside DataSources ..

I wrote a workflow to get the Network and set that property in VM, yet the ip seems to be already assigned . Seems that running this Vro as part of Pre Build Stub is not early enough

since Vra has already assigned the ip .

Question is how do i get this workflow to run earlier so that i can inject this property earlier in the process.