Public StrTier1, StrTier11 As String
Two things are wrong with what you posted vs. what you later said you needed.
1. Syntax: This should be
Public StrTier1 As String, StrTier11 As String
As you had it written, StrTier1 was a Variant. You can STILL assign a string value to it and it will work just fine - but it is VERY SLIGHTLY less efficient if your intent is that it would ALWAYS be a string and NEVER anything else. I suspect that the difference would only be detectable by timing two loops, each with an iteration count of 1,000,000 or so and each using one of the two definitions.
2. Semantics: Make it
Private StrTier1 As String, StrTier11 As String
(Or instead of Private you could use Dim, since Private is the default, I think.)
And as you have already acknowledged, this declaration must be in the declaration area of the module to be visible to the rest of the module.