How about using a macro to run the column autosize function?
I cheated, and recorded an autosize operation on a column, and then looked at the vb code behind the macro...
Columns("D:D").EntireColumn.AutoFit
should do the trick.
In the excelexamples.llb, they seem to use macros to perform other functions, so maybe this is a way to achieve the autosize function that you require.
Hope this helps...
JB