jjax,
As long as your boms are not too long this can be done using relations.
Replace the rpt.index parameter, in your bom table, with e.g. ItemNo
Go to Table, Repeat Regions, Relations
Create a simple relation at the command line, say ItemNo=1 and save it.
Edit the relation in pro tab, or whatever you use, to produce something like the following.
if <parameter_name>="value1"
ItemNo=1
else
if <parameter_name>="value2"
ItemNo=2
else
endif
endif
Extend the above to suit the bom, make sure to balance the "ifs" and "endifs", - cutting and pasting speeds things up a lot. Note that if the parameter name includes a period this must be replaced by an underscore, as shown above.
Sort the bom by the column ItemNo (Table, Repeat Regions, Sort Regions). As the parameter rpt.index is still associated with each item, the bom balloons will still work without modification.
Sorry if this is a bit long winded, but its not too bad when you do it!