BOA advise A to C

[Luiz Souza]

I have a SS in the final stages with BOA (my offer, B). There is not enough spread for a double, HML, etc. I do have a higher offer (C) on stand by to send to BOA. At this time I am just collecting a LM fee. When and how should I forward the higher offer to BOA so we don't start the process all over again? Should I wait until my offer gets accepted and then tell the negotiator the buyer walked however, we have another higher offer to present?
Thank you