custom alt tag for additional product images

Has anyone ever added custom alt attributes to their additional product pictures. I know I will involve an additional field to the database and customizing the theme, but I am not sure yet how to add a field to admin section of the admin section ->products ->image.

I imagine it will take adding a column to the table of something similar to that. Can anyone help or tell me how they did it.

thanks a lot guys

cool....thanks for the help