Pass Input-box String From Sub To Main

how to specify a file extension type for a browseforfolder part of what i've been doing.

It's not calling correctly as i'm not sure how to feed the inputData string back into the main.

Obviously there's probably better ways of doing this, but can my way be corrected easily?

I've been looking into ByVal and ByRef, but have only seen examples goin from main to the sub and not the other way.

Code:
Sub Main()
Dim strFolderName As String
Dim strFolderTest As String
Dim FRCntrHiLim As Variant
MsgBox "before calling inputbox"
Call InputBoxTest(inputData) '