Invalid Property Value with Calendar in VB6.0

Hi there, i am experiencing difficulties with my calendar in vb 6.0.

Private Sub Form_Activate()

sSelectedMonth = "January"
sSelectedYear = "2013"
cboMonth.ListIndex = 0
cboYear.ListIndex = 0

End Sub

I used the above code for my calendar but the error says "Invalid Property Value" with that code. Can you help me guys solve this problem? Thank's

Regards,
ImeehSajol