Null value filtering syntax help

I want a code like this:



DoCmd.OpenReport "rptPrecintosAGDLLA", acViewReport, , "[Username]='" & Me.[Username] & "'"



But after the "Me.[Username]" part, I want it to also filter to only show me data that has null values on a column called "PN".



Alternatively, I also need a code that instead of only showing me data that has null values, I want it to show me data that excludes the data with null values on the column called "PN".



Can this be achieved with this simple code, or do I need something more complex? Can you show me a syntax example? Thanks!

Null value filtering syntax help