Can VNC do this ?

[alunh]

I want to implement a PC screen sharing scheme as follows:

1 ) two PCs sharing a view of a single desktop. Call PC1, PC2 - and have assoicated users USER1 and USER2.

2 ) at all times both users can only view the desktop of PC1.

3 ) from start up USER1 is in control of the desktop.

4 ) using a keyboard command ( i.e. a function key for example) - USER2 can take control of the desktop from USER1.

5 ) using a keyboard command - USER2 can release control of the desktop back to USER1.

is this possible ?

Thanks

Alun