There isn't any way to define extra lines of text in an export.
I assume you are using the TransferSpreadsheet Method to export your query in fixed-width format. That's typically the right approach for generating the fixed-width content, with or without field headers.
But if you want to add lines to the file before and after the data content, then you'll need to open the existing file, create a new file, append the header lines, then append the data from the existing file to the new file, and then append the footer lines, then close both files.
You could use the built-in VBA functions for working with files, but I find the Scripting.Runtime library offers more intuitive, object-oriented ways of working with files.
You'll need to add a reference to the Microsoft Scripting Runtime library in Tools.. References..
Sub EnhanceExportedFile()
Const exportedFilePath As String = "C:\Foo.txt"
Const newFilePath As String = "C:\NewFoo.txt"
Dim fso As Scripting.FileSystemObject
Dim exportedFile As TextStream
Dim newFile As TextStream
Dim rowCount As Long
Set fso = New Scripting.FileSystemObject
Set exportedFile = fso.OpenTextFile(exportedFilePath, ForReading, False)
Set newFile = fso.CreateTextFile(newFilePath, True)
'Append the date in ISO format
newFile.WriteLine Format(Now, "yyyy-mm-dd")
'Append each line in the exported file
Do While Not exportedFile.AtEndOfStream
newFile.WriteLine exportedFile.ReadLine
rowCount = rowCount + 1
Loop
'Append the total exported lines
newFile.WriteLine rowCount
'Close both files
exportedFile.Close
newFile.Close
End Sub