Un-assign macros from all the checkboxes in Excel spreadsheet

I have an excel spreadsheet with more than 700 checkboxes. All the checkboxes have been assigned to one particular macro. I have deleted this macro. Now, I want to unassign this macro from all the checkboxes. I can do it for one checkbox manually by deleting the text when clicking on assign Macro. But how can I do this for large number of checkboxes? Any help greatly appreciated. Thanks!