See the article "How to create a Userform" at:

http://word.mvps.org/FAQs/Userforms/CreateAUserForm.htm

See the article "How to find out which Items are selected in a Multi-Select
ListBox" at:

http://www.word.mvps.org/FAQs/Userforms/GetMultiSelectValues.htm

Use a routine such as the following to load a multi-select listbox in the
userform with the data from your table

This routine loads a listbox with client details stored in a table in a
separate
document (which makes it easy to maintain with additions, deletions etc.),
that document being saved as Clients.Doc for the following code.

On the UserForm, have a list box (ListBox1) and a Command Button
(CommandButton1) and use the following code in the UserForm_Initialize() and
the CommandButton1_Click() routines

Private Sub UserForm_Initialize()
   Dim sourcedoc As Document, i As Integer, j As Integer, myitem As Range,
m As Long, n As Long
   ' Modify the path in the following line so that it matches where you
saved Clients.doc
   Application.ScreenUpdating = False
   ' Open the file containing the client details
   Set sourcedoc = Documents.Open(FileName:="e:\worddocs\Clients.doc")
   ' Get the number or clients = number of rows in the table of client
details less one
   i = sourcedoc.Tables(1).Rows.Count - 1
   ' Get the number of columns in the table of client details
   j = sourcedoc.Tables(1).Columns.Count
   ' Set the number of columns in the Listbox to match
   ' the number of columns in the table of client details
   ListBox1.ColumnCount = j
   ' Define an array to be loaded with the client data
   Dim MyArray() As Variant
   'Load client data into MyArray
   ReDim MyArray(i, j)
   For n = 0 To j - 1
       For m = 0 To i - 1
           Set myitem = sourcedoc.Tables(1).Cell(m + 2, n + 1).Range
           myitem.End = myitem.End - 1
           MyArray(m, n) = myitem.Text
       Next m
   Next n
  ' Load data into ListBox1
   ListBox1.List() = MyArray
   ' Close the file containing the client details
   sourcedoc.Close SaveChanges:=wdDoNotSaveChanges
End Sub

This is sort of what you asked for... (but I would do it Jonathan's
way if it were me.)

Instead of a Checkbox, which would require the document to be
protected, this routine uses a cell in column 1.

So, add a column and place a check (the letter X) in the row you want
to include in the second document.

Sub SelectCheck()
Dim aDoc As Document
Dim aDoc2 As Document

Dim aTable As Table
Dim MyRange As Range
Dim MyCell As Range

Dim NumRows As Integer
Dim A As Integer

Set aDoc = ActiveDocument
Set aTable = aDoc.Tables(1) 'Adjust to your table number
Set aDoc2 = Documents.Add

NumRows = aTable.Rows.Count

For A = 1 To NumRows
   With aTable
       'Get the contents of the first cell and see if there's a check
       Set MyCell = .Cell(A, 1).Range

       'Strip off the end of cell marker
       MyCell.MoveEnd wdCharacter, -1

       'If check found then paste it in the new Doc.
       If MyCell = UCase("X") Then
           .Rows(A).Range.Copy
           Set MyRange = aDoc2.Range _
           (Start:=aDoc2.Content.End - 1, _
           End:=aDoc2.Content.End - 1)
           MyRange.Paste

           'Clears the Check
           MyCell.Text = ""
       End If
   End With
Next A

End Sub

Hope this helps.
David