Issue is resolved. Apparently I was making it much harder than it really was. Below is the code for the Windows App and the Main DLL. This was my test, it worked and now I can put it into real action. My Main DLL will actually be processing large XML files into a database. The Windows App will pass to the Main DLL the XML file(s) the user chooses, the database connection variable, a ToolStripStatusLabel for progress update similar to the TextBox update below in my test and a TextBox for error information that might be encountered. Can't wait to test the real thing out.
Window App
Imports MainDLL
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myMainDll As New MainDLL.Class1
myMainDll.MyProcess(Me.TextBox1)
End Sub
End Class
Main DLL
Imports System.Windows.Forms
Public Class Class1
Public Function MyProcess(ByRef m_tb As TextBox) As Boolean
For x = 1 To 1000
m_tb.AppendText(x.ToString & Environment.NewLine)
Application.DoEvents()
Next
End Function
End Class