Get probability of one sentence conditioned on both prompt and suffix

I am wondering if GPT3 is capable of obtaining probabilities of a sentence given the prefix and suffix around the sentence.
Say a sequence of 5 sentences, sent1 sent2 sent3 sent4 sent5.
Is it possible to obtain the probability of sent3 given sent1 sent2 and sent4 sent5.
It seems a bidirectional feature while GPT3 is trained autoregressively so I am wondering if GPT3 can achieve that.
It seems that the new feature of GPT3 “Inserting text” can consider both prompt and suffix, so it wonder how GPT3 achieve that?

Thank you very much!

I tried to put sent1 sent2 sent3 in the prompt and sent4 sent5 as the suffix and create a completion job and it seems that I am not able to enable echo with suffix at the same time, is there possible to enable such features?