DirectX left to right handed system: matrix problem resolution

I am using a skinned model (with bones) from blender into my directx 9 program. The problem is that the model seems mirrored in my program. I tried to invert vertices position in the 3 axis by multipling by -1 the position and it works for the object itself but the bone matrices which are in their absolute position needs to be inverted too and here I am blocked. I tried to create a "-1,-1,-1" scaling matrix and multiply each bone matrix by it but it does not work as I expected. I need you to tell me how to do that. Thanks