Simple Calendar pop up macro --> error Run-time error '424': Object required

Hi there, I am attempting to get a "pop-up" Calendar to display however I am getting an error!

I am a little puzzled as to why, here is what I have:
One Workbook with five sheets, one form "frmCalendar, and one Module "Open_Calendar".

On sheet1 I select a cell and run the macro "Open_Calendar" result is: error Run-time error '424': Object required.

Form frmCalendar Code:

Please Login or Register  to view this content.

Module Open_Calendar Code:

Please Login or Register  to view this content.

Thanks for taking the time to read!

Works fine after fixing the typo. Thanks for the tip about "Require Variable Declaration." much appreciated!