Sub Main
    'Declare all needed variables
    Dim s, cs, y, w

    'Get all document's sheets
    s = ThisComponent.Sheets

    'Walk over all document's sheets
    For i = 0 To s.getCount()-1
        'Get the current sheet (cs stands for CurrentSheet)
        cs = s.getByIndex(i)

        'Get the year cell (here B5 cell)
        y = cs.getCellRangeByName("B5") 'Change here with year cell name

        'Get the week cell (here B6 cell)
        w = cs.getCellRangeByName("B6").String 'Change here with month cell name
        'If week number is lower than 10 add a leading "0" char
        If CInt(w) < 10 Then
            w = "0" & w
        End If

        'Change the current sheet's name with "yyyy-ww"
        cs.Name = y.String & "-" & w
    Next i
End Sub