If you get an error "Illegal function use: if(DTLINK:JOBS:CJOB_FEE_stocktickerKIND='flatfee')-dataset field CJOB_FEEstocktickerKIND not found" or similar while generating a new invoice, please try to disable all smart tags in MS Word.

On the Tools menu, click AutoCorrect Options, and then click the Smart Tags tab. Click "Remove Smart Tags", and then click Yes to confirm the deletion.

Note: Word removes the smart tags from your document. However, Word continues to mark new smart tags for any recognizers that are still active (those selected in the Recognizers list on the Smart Tags tab of the AutoCorrect dialog box).