i understand that you are occupied, but could you do me a favor to ...
比较客气的说法,不是命令语气
I know you are very busy, but could give me some time to do.....
I understand that you are busy, but could you please make some time (to do sth)
I know you are very busy,but would you pls spare some time to ......
I know that you are busy, but could you please spend some time doing sth.
我是从事英语的,不明再问啦。