Single method returning value to various projects

I define a method that gets the reason of a record exclusion and I return the reason typed by the user calling a public method in the caller Form.
I would like to use this method from various different projects.

In the called method I wrote for the first project:

if sender = projectA then
call projectA.public_method(reason typed by the user)

if I try to put an "else" like

else
if sender = projectB tehn
call projectB.Public_method(reason typed by the user)

I receive an error telling me that the projectB was not found.

How can I use the called method in various projects without use public variables in them?

Greetings from SãoPaulo - Brazil

Ricardo