Add-in Serious Error Message
 

I have a very large add-in that performs many complex tasks and calculations.
today I was adding code, and everything was going fine. I changed some code
that creates pull-down menus, saved the add-in *.xla file in the macro
editor, then closed Excel. When I reopened, I got a message "Excel
experienced a serious error the last time the add-in '****add-in name***' was
opened. Would you like to disable this add-in?....." I've tried many
things, but have not been able to reopen the add-in. How can I access the
code to try to correct the error?