Hi Richard,

Calculating the percentage change in Excel is actually quite simple. You can use a formula that combines the subtraction and division functions to calculate the percentage change between the old and new prices.

Here's how you can do it:

1. In a new column, subtract the old price from the new price. For example, if the old price is in cell A2 and the new price is in cell B2, you would enter the formula "=B2-A2" in cell C2.
2. Next, divide the difference by the old price. To do this, enter the formula "=C2/A2" in cell D2. This will give you the decimal representation of the percentage change.
3. Finally, format the cell as a percentage to display the result as a percentage. To do this, select cell D2, right-click and choose "Format Cells". In the Format Cells dialog box, select "Percentage" under the "Number" tab.

That's it! Now you have the net change and percentage of change for each part. You can copy and paste the formulas down the column to calculate the percentage change for all the parts.