Object variable or with block variable not set - VBA

Private Sub pusk_Click()
Dim opw As Object
Dim str As Object
Dim x As Variant
''''''' îòêðûâГ*ГҐГІ ГЄГ*ГЁГЈГі
 
If OptionButton1.Value = True Then
opw = per
End If
If OptionButton2.Value = True Then
opw = Application.GetOpenFilename( _
    "Excel files(*.xls*),*.xls*", , "ÂûáðГ*ГІГј Excel ГґГ*éëû", , True)
    If Not IsArray(opw) Then Exit Sub
End If
'''''''âûáèðГ*ГҐГІ Г*ГЄГІГЁГўГ*ГіГѕ Г±ГІГ°Г*Г*èöó
If OptionButton3.Value = True Then
str = Workbooks(opw).Worksheets(1).Select
End If
 
If OptionButton4.Value = True Then
x = ComboBox2.Value
str = Workbooks(opw).Worksheets(x).Select
End If
End Sub