(a)    Record of Excluded Evidence. If, during trial, an objection to a question propounded to a witness is sustained by the trier of fact, the examining attorney may make a specific offer of what the attorney expects to prove by the answer of the witness.

The court may add such other and further statement as clearly shows the character of the evidence, the form in which it was offered, the objection made, and the ruling thereon. The court on request must take and report the evidence in full unless it clearly appears that the evidence is not admissible on any ground or is privileged. The court may require the offer to be made outside the hearing of the trier of fact.

(b)    Filing. When documentary evidence is introduced in an action, the clerk or the judge must endorse an identifying number or symbol on it and when proffered or admitted in evidence, it must be filed by the clerk or judge and considered in the custody of the court and not withdrawn except with written leave of court.