Getting closer:
additions: find and copy the data into the "master" file
Sub Main()'THE MASTER FILE MUST BE SAVED IN THE FILE FOLDER
'ALONG WITH THE WORKBOOKS OF INTEREST
     Dim MyTempWB As Workbook
     Dim WS As Worksheet
     
'INFORMATION ABOUT YOUR FILE AND FOLDER
     Dim MyWB As Workbook
          Set MyWB = ActiveWorkbook
     ThePath = MyWB.Path
     MyWorkBookName = MyWB.Name
         
'LOOP THROUGH ALL FILES EXCEPT THE MASTER
     vPath = ThePath & "\*.xls"
     Filename = Dir(vPath)
     Do While Filename <> ""
          If Filename = MyWorkBookName Then GoTo SkipThisFile
     'OPEN NEXT FILE
          Workbooks.Open (CStr(ThePath & "\" & Filename))
          Set MyTempWB = ActiveWorkbook
     'STEP THROUGH EACH SHEET IN THE FILE
          With MyTempWB
               For I = 1 To CInt(MyTempWB.Sheets.Count)
                    'SEARCH THE SHEET FOR VALUE ItemID AND XItemID
                    Set ItemIDColumn = MyTempWB.Sheets(I).Cells.Find("ItemID", LookIn:=xlValues, LookAt:=xlWhole, SearchOrder:=xlByColumns)
                         If Not ItemIDColumn Is Nothing Then
                              FirstRow = MyTempWB.Sheets(I).Cells(ItemIDColumn.Row + 1, ItemIDColumn.Column).Row
                              LastRow = MyTempWB.Sheets(I).Cells(Rows.Count, ItemIDColumn.Column).End(xlUp).Row
                              Range(MyTempWB.Sheets(I).Cells(FirstRow, ItemIDColumn.Column), MyTempWB.Sheets(I).Cells(LastRow, ItemIDColumn.Column)).Copy
                              MyWB.Activate
                              Sheet1.Cells(Sheet1.Cells(Rows.Count, 1).End(xlUp).Row + 1, 1).Select
                              ActiveSheet.Paste
                              MyTempWB.Activate
                         End If
                    Set XItemIDColumn = MyTempWB.Sheets(I).Cells.Find("XItemID", LookIn:=xlValues, LookAt:=xlWhole, SearchOrder:=xlByColumns)
                         If Not XItemIDColumn Is Nothing Then
                              FirstRow = MyTempWB.Sheets(I).Cells(XItemIDColumn.Row + 1, XItemIDColumn.Column).Row
                              LastRow = MyTempWB.Sheets(I).Cells(Rows.Count, XItemIDColumn.Column).End(xlUp).Row
                              Range(MyTempWB.Sheets(I).Cells(FirstRow, XItemIDColumn.Column), MyTempWB.Sheets(I).Cells(LastRow, XItemIDColumn.Column)).Copy
                              MyWB.Activate
                              Sheet1.Cells(Sheet1.Cells(Rows.Count, 1).End(xlUp).Row + 1, 1).Select
                              ActiveSheet.Paste
                              MyTempWB.Activate
                         End If
               Next I
          End With
     'CLOSE THE FILE
          MyTempWB.Close
SkipThisFile:
     Count = Count + 1
     Filename = Dir()
     Loop
End Sub
Im positive that there is a better method, i just dont know it