I do similar things in dts

I would have the datapump task write a batch file and then execute the batch file to rename the file or files.

So write your excel sheet to a generic filename and then from a sql server connection to a textfile destination use the datapump task.

The datapump source is a select statement similar to the following

Select 'ren generic.xls ' + special + '.xls' txt

from table

The txt is just an alias that dts seems to require for the source to destination transformation.

The destination text file has 1 field as well named txt.

The last thing to do is to execute the batch file with the xp_cmdshell task.