Case FolderName + "\10Итог.xlsx"

Case s = Dir("\*Итог.xlsx")
           FolderName s

Workbooks.Open Filename:="C:\data\10Итог.xlsx"

Sub Макрос4()
    Selection.AutoFill Destination:=Range("H1998:H3183")
    Range("H1998:H3183").Select
End Sub

Function SUMIF_Extended(sheet1name$, sheet2name$, sumcell$, condcell$, condition) As Long
    On Error Resume Next: Application.Volatile True
    Dim WB As Workbook, sh As Worksheet: Set WB = Application.Caller.Parent.Parent
    sh1_ind& = WB.Worksheets(sheet1name$).Index
    sh2_ind& = WB.Worksheets(sheet2name$).Index
    For i& = sh1_ind& To sh2_ind&
        Set sh = WB.Worksheets(i)
        If sh.Range(condcell$).Cells(1) = condition Then
            SUMIF_Extended = SUMIF_Extended + Val(sh.Range(sumcell$).Cells(1))
        End If
    Next
End Function