Ask as soon as the trip is proposed. Counsel needs the receipt notice and the current admission record to answer, and if the advice is to wait, the employer needs enough notice to reschedule the meeting or send someone else.
Build the advice into the scheduling conversation
Include immigration review when the meeting is first proposed. A later decision on the pending request may change the analysis, but approval alone does not guarantee reentry or resolve every travel issue. Confirm the effective authorization and return route before booking.
If the trip cannot safely proceed on schedule, discuss remote attendance or another representative. Late questions are the mechanism behind most of these problems. Advice sought after the booking is advice about a decision already taken, and the cheapest moment to change plans has passed.
Put the question inside the scheduling conversation itself: before a date is proposed to anyone, ask counsel whether travel is prudent while this specific request is pending, and record the answer with its date. If the pending request has an expected decision window, write it beside the proposed travel dates so the conflict appears on one line. Hypothetical example: a greenhouse produce operation fixes a meeting date first and asks about travel afterwards, by which point moving the date has become the expensive option.