I have no idea what a domino circuit is so i'll be stupid and assume that the waveform you have shown you want delaying by 1/2 pulse. Do you have a clock running that has positive transitions in the middle of the positive pulses? If you do then use a simple D type latch with the clock fed to the clock input and the data (as shown on the picture) going to the D input. The Q output will be delayed by half of one pulse. Does this then give you enough time to latch V(sum)?
I've probabaly missed the point here and if I have please ignore my ramblings or downvote (with explanation to enable me to learn) as you see fit