Kettle Combination lookup step with dynamic key fields (Dimension field / Field in stream)

Pentaho Kettle

I need to dynamically set "Dimension field" and "Field in stream" fields in Combination lookup step of a transformation by using environment variables, it should be something like

Dimension field     |      Field in stream
__________
${dim_field}         开发者_JS百科|  ${field_in_stream}

Any ideas?

Create a new kettle plugin with the same code of combination lookup, in init method iterate over lookupFields and perform environmentSustitute for each field, that would give the possibility of input environment variables in lookup fields in kettle graphic step.