Welcome to the Community,
this won't unfortunately work, because Windows 7 doesn't support shared access to a volume. To use a volume from multiple hosts (like ESXi does this with VMFS data stores) it is required that the operating system is aware of this, which - as mentioned before - Windows 7 is not.
What you may do is to assign the virtual disk to only one of the Window 7 VM's, share the drive (or a folder), and map it through the network on the other VM.
André