Can't figure out this script Excel thing

[Webhead]

So I have this code here which is pretty basic...

Sub CopyToJoe()
'
' CopyToJoe Macro
'

'
    Range("A6:B6").Select
    Selection.Copy
    Sheets("Sheet2").Select
    ActiveSheet.Paste
    Application.CutCopyMode = False
    Sheets("Sheet1").Select
End Sub

So I'm trying to figure out what the syntax would be if I wanted to define a place in another workbook rather than just another sheet as it says by default (in red above).

I was thinking this all might work if it was something more like this...

Sub CopyToJoe()
'
' CopyToJoe Macro
'

'
    Range("A6:B6").Select
    Selection.Copy
    Sheets("Sheet2").Select
    ActiveSheet.Paste
    Application.CutCopyMode = False
    Sheets("=[main_file.xlsx]Sheet1!$B$6").Select
End Sub

I just can't figure out what the code is for that red part above.