There is a tendency to over complicate tables created to behave like spreadsheets. FormCalc is an extremely powerful tool that addresses these problems very nicely, and more importantly, easily.
For example, consider a footer row and a calculated - read only field called 'fixedCostTotal',
// form1.page1.subform1.table.footer.fixedCostTotal::calculate - (FormCalc, client)
$.rawValue = sum(form1.page1.subform1.table.row[*].fixedCost)
Take a look at the attached and see if it helps.
Steve