請問幾時用by tomorrow 幾時用on tomorrow?

By tomorrow = not later than tomorrow
Example : I will hand in my home work by tomorrow. - This sentence does not tell the reader whether you have finished your home work now, you just tell the reader that you will hand in your home work tomorrow
On tomorrow = the action you are going to take will definitely be done on tomorrow
Example : I will clean up my room on tomorrow. - This sentence tells us that you have not cleaned up your room now, but you will clean up tomorrow.
Note : We do not use "on tomorrow" very often. The "on" can be omitted in most cases. Just like above example :
I will clean up my room tomorrow - this has the exact meaning of "I will clean up my room "on" tormorrow.

"by tomorrow" = 聽日之前

"on tomorrow" 如果唔洗用"on"; 唔知邊個補習天王教你呢?

例如: 我聽日會做那件事. I will do that tomorrow.
(無"on")

2008-08-18 14:28:22 補充：
我想講, 通想無"on", 只係打錯字!