You cannot do this directly in SSRS. but there is a work around if you wish to proceed.
1. generate your files in folder.
2. create SSIS Package and add script task.
3. write C# code to program your needs on each file.
oExcel = CreateObject("Excel.Application")
oExcel.Visible = False
oBooks = oExcel.Workbooks
oBook = oBooks.Open(Dts.Variables("filePath").Value.ToString())
//Your macro here:
oExcel.Run("Yourmacro")
you can use above code as well...