Convolution from bottom right
I hope I understand your question correctly, in that you're trying to produce a mirror image of the convolution kernel (filter) and then convolve. Flip you convolution kernel. In MATLAB, you can use the flip command. If you flip it left-to-right, this should do it.

However, if you're simply saying that you want to use the same kernel but start the convolution process from a different point, this would not give you a different result back at all. This is one of the reasons you can do FFT based convolution.