(a) Where the attorney of record for any party arranges for another attorney to conduct the trial, the trial counsel must be identified in writing to the clerk and to all parties not less than 15 days before the date assigned for trial. The notice must be signed by both the attorney of record and the trial counsel and filed with the clerk.

(b) After trial counsel is designated as provided above, no substitution shall be permitted unless the substituted counsel is available to try the case when it is reached in regular order. Written notice of such substitution shall be promptly filed with the clerk and given to all parties.