Actually what you need to do is INSERT the paragraph when the field has value. The field will presumably have a monetary amount or zero or nothing. The following assumes a monetary amount or nothing. The plan therefore is to add the condition to the end of the previous paragraph. In autonumbered paragraphs the sequence will look a little odd - as shown in the screenshot, but it all works itself out and the numbering will be correct when the merge is run.

Example.jpg