Hi
If i understood well your doubt, you can change width in percentage for all main template blocks on template parameters.
For example, take in consideration the screenshoot:
screen_2011-05-04.png
Width page value is set in pixels (910px)
The Left column will have 26% of full template width (something like 237px)
The Left 2 width will have 50% of Left Column width = 118px.
Naturally, Left 1 position will have the difference.
In this case, Left Top width will be the
same as set on Left Column width value.
Hope this is well explain.
Cheers