A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
You can't use &[UserName] - it won't be recognized. But you can use the BeforePrint event of the workbook (in the ThisWorkbook module) to set the header or footer using VBA. For example:
Private Sub Workbook_BeforePrint(Cancel As Boolean)
Dim wsh As Worksheet
For Each wsh In Me.Worksheets
wsh.PageSetup.CenterFooter = "Printed on &D at &T by " & Environ("Username")
Next wsh
End Sub