New release 0.2.0 of OneClickETL script is available for
download (look for file OneClickETL-0.2.0.tcl) from OWBLand Sourceforge project.
OneClickETL script automatically generate mappings based on specification from Excel file (rules for prepearing Excel file described in previous OneClickETL-related articles -
http://owbeg.blogspot.com/2010/11/prototype-oneclicketl-script.html and
http://owbeg.blogspot.com/2010/11/oneclicketl-release-011.html).
Now last release support column expressions - in mapping specification worksheet (in column B where earlier was source columns) it is possible to specify expression over columns (you can even insert standard Oracle function/stored function call).
See screen snapshots with example of expressions in Excel file and generated mappings:
Another example (for SCD Type 1 mapping type):