CloverETL is primarily a tool for data manipulation. It can implement business rules that extract information from source systems and transform it to business knowledge. Apart from Excel file, CloverETL can create HTML, Text, and XML and CSV outputs of your data using the StructuredWriter or the XMLWriter components.
Anyway, CloverETL GUI is an Eclipse plugin and thus "embeddable" into any other Eclipse application, e.g., an application providing a nice graphical layout to your report.