I'm going to remind you of Standing Order 62, which appears on page 223 of the Annotated Standing Orders. This Standing Order normally applies to the proceedings of the House, but you'll understand that it can also apply to committee proceedings.
Standing Order 62 reads as follows:
When two or more Members rise to speak, the Speaker calls upon the Member who first rose in his or her place; but a motion may be made that any Member who has risen “be now heard”, or “do now speak”, which motion shall be forthwith put without debate.