Alter table Permission

Hi All
I need to give following permission to a user

• Read and Write on all objects
• Alter Table permission on 5 tables

Read and write are given by db_datareader and db_datawriter. But how i give ALTER table permissions...I do not want to use db_ddladmin.
I have search the site but could not locate anything about it.. used GRANT ALTER Table to Username.. command but didn't work...
Thanks in Advance

Try this:grant
alter on <your table> to [<your database user>]

I have tried this before but got following error
Incorrect syntax near the keyword 'on' .

But the sql statement is 100% right..!!

Hi
I have checked and statement is correct but I wonder that why didn't worked... Please help...