private double verifyInput(int row, int column) {
        String value = model.getValueAt(row, column).toString().replace(",", ".");
        Double hours = 0.0;
        if (Utils.isNumeric(value)) {
            hours = Double.parseDouble(value);
        } else if (value.equalsIgnoreCase("v")) {
        } else if (value.equalsIgnoreCase("z")) {
        } else if (value.equalsIgnoreCase("c")) {
        } else if (value.equals("*")) {
        } else {
            Utils.showMessage("Fout opgetreden, foutieve invoer (" + value + ") in veld (" + row + ", " + column + ")", "Fout!", null, false);
        }
        return hours;
    }