I'll add my vote of support for using Excel to automate designs, especially if you don't want to be reliant on "black box" design software. It's really not so difficult, especially if you've done it once by hand. Just put in your spreadsheet what you did in your hand calcs.
Following a few simple steps will make it much easier to use over again:
1) All input values, including load and resistance factors, are entered into cells and reference those cells in the equations. The only numbers that should appear in a formula are constants that are in the equations you're using.
2) Mark your input cells. I shade mine so I can tell at a glance the cells I may need to change the values in.
3) Use tables whenever possible, and then return values from the tables using either the Vlookup function (easiest) or a combination of Index and Match functions (more versatile, but a little more difficult). For instance, if you're using a number of rolled shapes, you can table the section properties, with a reference value in the left column of the table, choose one using the reference value input into a cell, and then use the Vlookup function anywhere you need one of those properties. You can use the name of the section as the reference value, but you must match it exactly when you input it. I find it easier to just number the sections. Alternately, you can use a drop-down box, but that is more advanced.