These variables  are being declared here, and have scope only within the
Sub.

They are built to pass arguments into the sub alone and if you want to
keep them globally, it's best to just pass global values to them. Let me
give you a little analogy in code:

----start of module
Global str_gl_Colour as String
Global str_gl_Animal as String
Global str_gl_Sentence as String
----
Sub CallString
str_gl_Colour = "Yellow"
str_gl_Animal = "Dog"
MakeString(str_gl_Colour, str_gl_Animal)
End Sub
----
Public Sub MakeString(myColour, myAnimal)
str_gl_Sentence = "I would love to own a " & myColour & " " & myAnimal
End Sub
----end of module