行いきがけの駄だ賃ちん

expression

while you're at it; taking the opportunity; on the way

Idiomatic expression meaning to do something incidentally or while already engaged in another activity, often implying making good use of the opportunity. Can be used literally for doing something en route, or figuratively for any convenient chance.

• 買かい物ものに行いくなら、行いきがけの駄だ賃ちんに郵ゆう便びん局きょくにも寄よってきて。

  If you're going shopping, stop by the post office while you're at it.

• 出しゅっ張ちょうの行いきがけの駄だ賃ちんで、ついでに観かん光こうもしてきた。

  I took the opportunity of the business trip to do some sightseeing on the side.