Find last row

I need to find the last row of data, where the last data entry may be in different columns. I had been using this code, thinking that column B would contain the last data entry. This isn't always the case.

Dim LastRowCopy As Long, LastRowPaste As Long
  
    LastRowCopy = Sheets("PCR Summary").Range("C" & Rows.Count).End(xlUp).Row               ' Last used row on "PCR Summary"
    
    Sheets("PCR Summary").Range("A1", "E" & LastRowCopy).Copy _
        Destination:=Sheets("PCR Parts Summary").Range("A1"

I tried modifying the LastRowCopy line to say:

 LastRowCopy = Sheets("PCR Summary").Range("A:F" & Rows.Count).End(xlUp).Row               ' Last used row on "PCR Summary"

but I get an error, Run-Time Error '1004, Application-defined or object defined error.
...anyone? Thanks in advance.