Need Help with Error Message

Code:

---

Public const AllowedTime As Double = 120 'Number of minutes to count down

---

When I try to run the above code I get a compile error that states:

Quote:

---

Compile Error:
Constants, fixed-length strings, arrays, user-defined types and Declare statements not allowed as Public members of object modules

---

I saw this code on another forum which seemed to work with other users. I running Excel 2010. thank you.

declare it in a standard module.
why double ?