how to align the comments to start from the same column?

["William Xue" <william.xue@gmail.com>]

Hi,
when I am coding in cpp files, I will use M-; to make some comments, like  
following:

                         IoCreateFileSpecifyDeviceObjectHint(&h_rd_file, //  
file handle
                                                             GENERIC_READ |  
GENERIC_WRITE, // desire access
                                                             &rd_file_obj_attr,  
// object attributes
                                                             &rd_io_status_block,  
// io status block
                                                             0, //  
allocation size
                                                             FILE_ATTRIBUTE_NORMAL,  
// file attributes
                                                             FILE_SHARE_READ,  
// share access

Is there a way to format the comments to the same column?

I want something like:

1. select the codes as a region
2. press a magic keybinding
3. the comments align to the longest column of comments in the region.

:)

-- 
Sincerely yours,
William