For RIA, it is more appropriate to have fluid layout for application as there are many different resolution for different user’s computer.

Flex’s datagrid, however, its column does not support dynamic width.

I do tried to use actionscript to set those width during runtime like using onCreationComplete or onResize of the datagrid, sadly that it is unable to control the width of columns, keep being feeded with some float values.

Until Dave suggested a over-simplified solution: to use decimal number for the width value:
http://www.daveoncode.com/2009/03/18/set-datagridcolumns-width-in-percentage-with-ease/

It is really crazy simple, with spent me lots of time in brain-storming other useless AS3 solutions……