1 sentence for 正当 (zhèng​dāng — just when)

1. 正当他在电脑上工作时，来访者进来了。

   zhèng​dāng tā zài diàn​nǎo shang gōng​zuò shí, lái​fǎng​zhě jìn lai le.

   While he was working on his computer, a visitor came in.

   Source: UM-Corpus: Education