It is simply a matter of moving the range as appropriate e.g.
Code:
Sub Macro1()
Dim Ff As FormField, Rng As Range
Dim MainTable As Table
Set MainTable = ActiveDocument.Tables(1)
Set Rng = MainTable.Cell(14, 1).Range
Rng.End = Rng.End - 1
Rng.Text = "This is some text "
Rng.Collapse 0
Set Ff = Rng.FormFields.Add(Rng, wdFieldFormCheckBox)
lbl_Exit:
Set Rng = Nothing
Set Ff = Nothing
Exit Sub
End Sub
Personally I would recommend using content controls rather than form fields so
Code:
Sub Macro2()
Dim CC As ContentControl, Rng As Range
Dim MainTable As Table
Set MainTable = ActiveDocument.Tables(1)
Set Rng = MainTable.Cell(14, 1).Range
Rng.End = Rng.End - 1
Rng.Text = "This is some text "
Rng.Collapse 0
Set CC = Rng.ContentControls.Add
With CC
.Type = wdContentControlCheckBox
.Tag = "Check1"
.Title = .Tag
.Checked = False
.LockContentControl = True
End With
lbl_Exit:
Set Rng = Nothing
Set CC = Nothing
Exit Sub
End Sub