Fernando,
This may not be directly related, but thought it would be worthwhile to share. I recall having to work on a SQL DTS package to import data from Excel to SQL Server. I was experiencing problems with some of the values getting transformed to NULL and couldn't figure out why until I read the following article:
http://www.sqldts.com/default.aspx?6,222,254,0,1Laterness,
Jon
Jon Rosenbaum
Devcon Drummer