I don't know why the following code keeps coming back as a runtime error 13, type mismatch; I have checked the code several times and I can't find the problem - can anyone help me?

Option Explicit
Sub cmdclick()

Dim app As Application
Dim wkbk As Workbook
Dim shtctrl As Worksheet

Dim StarName As String

Set wkbk = ThisWorkbook
Set app = wkbk.Application
app.ScreenUpdating = False
Set wkbk = ThisWorkbook
Set shtctrl = wkbk.Worksheets("Control")

StarName = wkbk.Path & "\" & "STAR Week No " & _
wkbk.Names("WeekNo").RefersToRange.Value & " " & _
Format(wkbk.Names("ControlDate").RefersToRange.Value, "mmm dd yy")

MakeSTAR StarName

MsgBox "Finished"

End Sub