Pivot Tables - Calculate and filter

[AntMac]

I am trying to create a pivot table with Base data like this below. I am trying to now add a ratio of PM to demand and filter for assets where this ratio is high or low. I can get the table to display each percentage but every filter I try doesn't seem to work. Can this be down outside of adding additional columns with calculations in the source data?

[TABLE="width: 500"]
<TBODY>[TR]
[TD]Asset[/TD]
[TD]PM/DM[/TD]
[TD]Cost[/TD]
[/TR]
[TR]
[TD]One[/TD]
[TD]PM[/TD]
[TD]100.50[/TD]
[/TR]
[TR]
[TD]One[/TD]
[TD]DM[/TD]
[TD]200.75[/TD]
[/TR]
[TR]
[TD]Two[/TD]
[TD]PM[/TD]
[TD]25.65[/TD]
[/TR]
[TR]
[TD]Two[/TD]
[TD]DM[/TD]
[TD]35.80[/TD]
[/TR]
[TR]
[TD]Two[/TD]
[TD]PM[/TD]
[TD]46.90[/TD]
[/TR]
</TBODY>[/TABLE]