>It work for me for all type of columns (string, date, numeric, etc.) But I use this from VFP.

Ok, but this is because you are using an OLE approach. Thus, you are building the sheet as if you would be sitting in Excel. Thus, Excel knows the width and can adjust it. For example, if you save as XML, you will see it has hardcoded the width value for every cell. But, when you generate the XML, you cannot benefit from that approach. Only when the document is opened, and I go set the width to be autofit, after another save, there I can have the auto width to be ok, but this is because it has calculated the width value when I was adjusting its layout when I was in Excel.