Hbridge current limiting

Please help me with this design as i am stumped as to how i should limit the current going through the mosfets.

the design is 300vdc on the mosfet and i want to limit the current to 3 amps. I dont want to switch the drivers off and wait for the current to dissipate becuase if i do this then the circuit wont switch on because the current draw will be 3 amps. using the sd pin according to the datasheet will switch off the mosfet until the current subsides below the limit.So my reasoning is that if the circuit draws 3 amps then it will switch off am i correct with this or am i seeing it wrong. Furthermore if i can limit the current draw to three amps then the circuit will draw three amps only no more and the circuit should work.

please advise me on what you think.

also I am not stuck with this design so any suggestion on another design that would work is good.

the circuit.
I am pulsing the mosfetson for 2 secs then off for .5 secs then pulsing the other mosfets on for 2secs etc.

Are you driving a motor?
You want to limit to 3A but you start-up current is 3A???
How fast to you want to to into current limit? uS or mS

1)Current limit could switch off the MOSFETS
2)Current could cause the MOSFETs to open up and go into linear mode, where they pull 3A but have 200 volts across them. (hot FETs)

Lift the Source pins from the bottom two FETs. Q2,3. Connect the sources together. Add 0.2 ohm resistor to VSS2. When the current reaches 3A the voltage will reach 0.6 volts. Add a 2N2222a. Emitter on VSS2, Base connects to 100 ohms. 100 ohms to the sources of Q2,3. Now the 2N2222 will turn on when the current is too high. Now what to do????? ISO-Opto back to the micro so It can turn off the FETs.

Is Vss2 ground?
If so you could use Ron's idea but just tie up the SD pin and pull it low with the 2N2222.

RonV, The bridge is isolated.

hi ron
if i lift the source pins of the two bottom fets the power flowing in the circuit would be by equation P=IV therefore 3 X 300 =900 therefor wouldnt the resistors have to be 900 watts ?

Ahh, I see it over there now.
You only need to drop .6 volts across the resistor to turn on the transistor to limit the current so it is 3 X 0.6 or 1.8 watts. The rest is used in the load.