Could you cover for me on Tuesday? I'm not coming back until Wednesday. 你星期二可以帮我代班吗?我要到星期三才回来。

Sure. What's up? 当然可以，有什么事吗?

He substituted for his colleague who was ill. 他为生病的同事代班。

Rose will cover for me while I'm away. 我不在的时候，罗斯会帮我代班。

My colleague agreed to cover for me during my vacation. 我的同事答应我休假的时候帮我代班。