//Add data
for (var col = 1; col < 6; col++) {
    for (var row = 2; row < 11; row++) {
        activeSheet.setValue(row, col, row + col);
    }
}

var sTable = activeSheet.tables.add("table1", 1, 1, 10, 5, GC.Spread.Sheets.Tables.TableTheme.medium2);
sTable.showFooter(true);
//set footer value
sTable.setColumnValue(0, "Total");
//set footer formula
sTable.setColumnFormula(4, "SUM(F3:F11)");
var value = sTable.getColumnFormula(4);
alert(value);