combine multiple workbooks in one excel-workbook - excel

Question

I want to combine the first sheet of multiple workbooks into one master workbook. The data is always structured in the same manner. In addition to this, I want an extra sheet in my master workbook where all the data is summarized (to add up all the numbers of each sheet,eg 1+1+1=3).
So far I started with this code. Yet, I have no idea how to summarize in VBA with different workbooks (that is why it not included in the code)
thanks in advance folks!
'Defining
Dim wb As Workbook
Dim ws As Worksheet
Dim directory As String
Dim myFiles As String
Dim targetwb As Workbook
Set targetwb = ThisWorkbook
Application.ScreenUpdating = False
directory = "C:\Dokumente\"
myFiles = Dir(directory & "*.xlsx")
'Loop through all files in a folder until DIR cannot find anymore
Do While myFiles <> ""
'Open Workbooks one by one 'Do i really have to use the "set command"???
Set wb = Workbooks.Open(Filename:=directory & myFiles)
'The actual action
'Countries:
'Brazil:
If wb.Name = "Brazil*" Then
Worksheets("Status Overview").Copy ThisWorkbook.Worksheets("Brazil")
End If
'Kosovo:
If wb.Name = "Kosovo*" Then
Worksheets("Status Overview").Copy ThisWorkbook.Worksheets("Kosovo")
End If
'United States:
If wb.Name = "United States*" Then
Worksheets("Status Overview").Copy ThisWorkbook.Worksheets("United States")
End If
Workbooks(myFiles).Close
myFiles = Dir
Loop
Application.ScreenUpdating = True```

Answer 1

Run this in a Workbook with one sheet name Summary.
Option Explicit
Sub Summarize()
Const FOLDER = "C:\Dokumente\"
Const WS_NAME = "Status Overview"
'Defining
Dim wbIn As Workbook, wb As Workbook, ws As Worksheet, ar, s
Dim filename As String, msg As String
Dim copied As Collection
Set copied = New Collection
ar = Array("Brazil", "Kosovo", "United States")
Set wb = ThisWorkbook
'Application.ScreenUpdating = False
filename = Dir(FOLDER & "*.xlsx")
Do While filename <> ""
For Each s In ar
If LCase(filename) Like LCase(s) & "*" Then
Set wbIn = Workbooks.Open(FOLDER & filename, True, True) ' update links, read only
wbIn.Sheets(WS_NAME).Copy after:=wb.Sheets(wb.Sheets.Count)
wbIn.Close False
wb.Sheets(wb.Sheets.Count).Name = s
copied.Add s
msg = msg & vbCrLf & s
End If
Next
filename = Dir
Loop
' build =SUM() formula
Dim f As String, sep As String, rng As Range
f = "=SUM("
For Each s In copied
f = f & sep & "'" & s & "'!RC"
sep = ","
Next
f = f & ")"
' range to summate on summary sheet
Set rng = wb.Sheets("Summary").Range("A10:E20")
' apply sum formula to range
rng.FormulaR1C1 = f
'Application.ScreenUpdating = True
MsgBox "Imported :" & msg, vbInformation
End Sub