Further to JT's posts:
Let's assume that you have a bit of paper with W&B stuff that you have written in it which conforms to the approved loading system. If that approved loading system requires that you use arithmetic then it is your responsibility to do that arithmetic and ensure that it is correct.
You may do the sums in your head or by long multiplication counting on your figures or use an electronic calculator. You may use Excel iff you check the cell contents are correct wrt data and calculations every time i.e. treating Excel as a simple calculator.
Grabbing an Excel worksheet and just typing in the specific loading configuration or using the W&B functions in the popular iPad Apps - then carefully read the appropriate section in the CASA CAAP on Electronic Flight Bags.