::You see, I build the table in code, cell by cell so I don't specify the width of the table.

Even by that means you still have the ability in .NET to set the table with, just as you do the cell width at the lower level.



::I need to create the images (e.g. cellpic.gif) of the size exactly equal to the width of the column.

There's your answer then. Don't specify the cell width at all, and let your image be the spacer.