This did the trick for me.I had found suggestions about workflow setting, schema readers, etc;none of them worked.I have a workbench on FME Server that people feed their Excel into.Two attributes are fixed, but the user can add additional attributes they want to see in their shapefile.It took me a few tweaks to get the parameters right, but setting Features to Read = Schema and Data Features and Accumulation Mode = Only Use Result took care of it.The output changes schema as different spreadsheets are read in.
Thanks for the question and answer.
I suggest you use the transformerCreatorto Start your Workpace and after use the transformerFeatureReaderto extract dynamic values between your two ( 2 ) files:
Thanks,
Danilo