Where the code is located depends on the kind of command button, forms or activex control. Posting a short sample workbook would help me help you better. You can manually add the new sheet with the output expected.
In any case, one typically puts Functions into a Module.
Why don't you test the code as I suggested to see if it will get what you need? Putting the result in column A of a new sheet is trivial. I can show that to you later.
Put all of this in a Module. Then run the Test sub. Of course you need to run it with the sheet active that has the correct value of cell E4. After you run it, review VBE's Immediate Window for the results of Debug.Print.
You may need to change the Value2 to Text if E4 is formatted date. I put the result of FileFolder into the Immediate window with Debug.Print so you can check if the FileFolder string was correct.
Sub Test_SearchFiles()
Dim v As Variant, a() As Variant, FileFolder As String
FileFolder = "\\sptd.sabert.net\sites\op\olt\Production Supervisors\HouseKeeping\Completed_Checklist\" & Range("E4").Value2 & "\"
Debug.Print "FileFolder = ", FileFolder
'FileFolder = ThisWorkbook.Path
SearchFiles FileFolder, "*.*", 0, a(), False
'Debug.Print UBound(a(), 1), UBound(a(), 2)
For Each v In a()
Debug.Print v
Next v
End Sub
' Returns 2 dimension array. e.g. a(1,1)=Path, a(2,1)=Filename
Function SearchFiles(myDir As String _
, myFileName As String, n As Long, myList() _
, Optional SearchSub As Boolean = False) As Variant
Dim fso As Object, myFolder As Object, myFile As Object
Set fso = CreateObject("Scripting.FileSystemObject")
For Each myFile In fso.getfolder(myDir).Files
Select Case myFile.Attributes
Case 2, 4, 6, 34
Case Else
If (Not myFile.Name Like "~$*") _
* (myFile.Path & "\" & myFile.Name <> ThisWorkbook.FullName) _
* (UCase(myFile.Name) Like UCase(myFileName)) Then
n = n + 1
Redim Preserve myList(1 To 2, 1 To n)
myList(1, n) = myDir
myList(2, n) = myFile.Name
End If
End Select
Next
If SearchSub Then
For Each myFolder In fso.getfolder(myDir).subfolders
SearchFiles = SearchFiles(myFolder.Path, myFileName, _
n, myList, SearchSub)
Next
End If
SearchFiles = IIf(n > 0, myList, CVErr(xlErrRef))
End Function