I've been in this exact situation. Client provides their current workflow, implemented in a spreadsheet. The problem is they make significant concessions in th

I've been in this exact situation. Client provides their current workflow, implemented in a spreadsheet. The problem is they make significant concessions in their design to fit the tabular model of spreadsheets. It can be really warping, not only to GUI but also the underlying data model. Then you show them what a relational data model is capable of, and (hopefully) blow their mind.