Price Variance Bar Chart

[#1]

Dear Community

I wonder how can I build a Price Variance Bar Chart in Qlik Sense. It is to show the Percentage price variance between Current unit price and Last PO price for parts.  [ ( Current Unit price - Last PO price ) / Last PO price ] x 100%

The result I want is as follows.

(Even part no. TYU2435 ordered twice in the Jan, I want to use $2500, the Last PO price, to calculate.)

However, I don't know how to build it in Qlik sense. As I already set:

Dimensions: Part No.

Show in percent

Static max 1, min -1

How can I set the expression in Measures?

Thank you very much. Please give me a helping hand.