Error when passing workbook object to VBA form - excel

Question

I am working on a VBA script with Microsoft Word that allows the user to select text that will be copied to the clipboard so that it can exported to an Excel file. The user will make a number of selections and finally indicate he/she is done when the contents of the clipboard will be copied to a template Excel file.
The form (frmModeLessForInput) is a modeless form. The form has two buttons "Continue" and "Done". The user is allowed to navigate the document and place the cursor anywhere in the document. Then when "Continue" is pressed the form will call a subroutine (Highlight_Sentence) to copy the selected text to a "clipboard" variable. When "Done" is pressed control will be passed to called subroutine which will then copy the clipboard to the Excel file.
The problem I am having is that I don't seem to have correct code needed to pass workbook object in created in the MAIN MODULE to the form using a form property.
Below is the code. I have inserted comments in the code in the Select_Sentence_Form_Test and cmdDone subroutines where I am having the problem passing the workbook object.
Any assistance in resolving these problems is appreciated. As VBA programming is a sideline for me I am still learning.
Option Explicit
Public str_clipboard As String
Public txt_active_document As String
Public i_how_many_sentences As Integer
Public str_active_document
Public str_Excel_Filename As String
Public i_starting_row_ID As Integer
Public i_rows_of_data As Integer
MAIN MODULE
Sub Master_Module_Test()
Dim oExcel As Object
Dim wb As Excel.Workbook 'Object
Set oExcel = New Excel.Application
str_Excel_Filename = "C:\Test\Excel_Template.xlsx"
Documents.Open ("C:\Test\Doc_to_process.docx")
oExcel.Workbooks.Open str_Excel_Filename
i_how_many_sentences = 0
i_starting_row_ID = 1
Set wb = ActiveWorkbook
Call Select_Sentence_Form_Test(wb)
End Sub
Sub Select_Sentence_Form_Test(wb_open As Workbook)
Dim frm As frmModelessForInput
Set frm = New frmModelessForInput
' At this point wb_open is instantiated, i.e. I get "Excel_Template.xlsx" for wb_open.name
' But this code gives me an error "Object or block not set". If I leave this statement out then "Me.Book1.ActiveSheet.PasteSpecial..." in cmd_Done in the frmModelessForInput module gives the same error
Set frmModelessForInput.Book1 = wb_open
With frmModelessForInput
.str_word_doc_filename = str_active_document
.str_no_copied = "0"
.Show False
End With
Set frm = Nothing
End Sub
Below is the code for the frmModelessForInput form
Option Explicit
Private m_Book1 As Workbook
Public Property Get Book1() As Workbook
Set Book1 = m_Book1
End Property
Public Property Set Book1(ByRef Value As Workbook)
Set m_Book1 = Value
End Property
Private Sub UserForm_Activate()
'Position the form near the top-left of the window
'So that the user can work with the document
Me.Top = Application.ActiveWindow.Top + 15
Me.Left = Application.ActiveWindow.Left + 15
End Sub
Private Sub cmdContinue_Click()
Dim str_clipboard, str_clipboard_line As String
Call Highlight_Sentence(str_clipboard_line)
i_how_many_sentences = i_how_many_sentences + 1 'Problem: VBA reports i_how_many_sentences as undefined even though it is a Public variable
frmModelessForInput.str_no_copied = i_how_many_sentences 'Same Problem
str_clipboard = str_clipboard + str_clipboard_line 'Problem: each time I select a new text/sentence str_clipboard does not contain the contents of the previous selection
End Sub
Private Sub cmdCancel_Click()
b_abort = True
Unload frmModelessForInput
End Sub
Private Sub cmdContinue_Click()
Dim str_clipboard_line As String
Dim i_row_number As Integer
i_row_number = i_how_many_sentences + i_starting_row_ID
i_how_many_sentences = i_how_many_sentences + 1
Call Highlight_Sentence_Test(str_clipboard_line, i_row_number)
frmModelessForInput.str_no_copied = i_how_many_sentences
str_clipboard = str_clipboard + str_clipboard_line
End Sub
Private Sub cmdDone_Click()
' When the "Done" button is pressed the contents of the str_clipboard variable is copied to the Windows clipboard
Dim str_filename As String
str_filename = getName(str_Excel_Filename)
MsgBox "I will now copy the data to the Excel file."
Call SendToClipboard(str_clipboard) 'This sub puts the contents of str_clipboard into the Windows clipboard
' Uses the Book1 property --- this is the code line that produces the error "Object or block variable not set. Activeworkbook.name shows that Excel_Template.xlsx is active
Me.Book1.ActiveSheet.PasteSpecial Format:="Text", Link:=False, DisplayAsIcon:=False, NoHTMLFormatting:=True
Unload frmModelessForInput
MsgBox "Done pasting data to: " & getName(str_Excel_Filename)
End Sub
Private Sub Highlight_Sentence(clipboard As String, i_row_no As Integer)
Dim txt_sentence, txt_page_no As String
Dim txt_section_index As String
With Selection
' Collapse current selection.
.Collapse
' Expand selection to current sentence.
.Expand Unit:=wdSentence
End With
clipboard = i_row_no & vbTab & txt_sentence & vbCrLf
End Sub