High side Switch-Urgent!

Hi
Could any body please help me with the following problem (You could
write in German :-)):

I have a circuit configured as shown in figure1.Network-1 charges  the 
capacitor from 0V to 350V (part1 in Fig.2) and  discharges it(part2 in 
Fig.2)
Network-2 charges & discharges the capacitor from 0V to -100V(part 4 in 
Fig2) and vice versa(part 3 in Fig2).
During the operation of the network-1(parts 1&2), network-2 must be 
completely disconnected from the capacitor and similarly the network-1 
must be completely disconnected, while the network-2 is working(parts 
3&4).

* charging & discharging period is about 12.5ms(80Hz).
* The connection & disconnection of the networks must happen in a very 
short time.
*current flows in both directions in the path between networks and the 
capacitor.

For this reason I selected switch-1 (MOSFET, N-channel) between 
network-1 and the capacitor and switch-2(MOSFET, P-channel) between 
network-2 and the cap.(for both switches source is connected to the 
cap.).

switch-1 must be on during parts 1&2.It's source is floated and can 
reach a voltage about +350V.It must be off while network-2 is 
working(parts 3&4), where the source experiences a floating voltage from 
0V to -100V.
Also,switch-1 must have a max-Vg>350V during parts 1&2 and min-Vg<-100 
during parts 3&4.
A similar investigation for the switch-2 results in a min-Vg<-100 during 
parts 3&4 and max-vg>350v during parts 1&2.


How can I realize  drivers for these switches?Drivers must be very small 
and dissipate ultra-low power.
Or any other Idea to realize the switches, except using MOSFETs?


I'll be gratefull if any body can help me with this problem!
thank you very much in advance