The following will write sentences containing 'the supplier', regardless of case, to a new document.
Code:
Sub Macro1()
'Graham Mayor - https://www.gmayor.com - Last updated - 25 Sep 2019
Dim oSource As Document
Dim oTarget As Document
Dim oRng As Range, oTargetRng As Range
Set oSource = ActiveDocument
Set oTarget = Documents.Add
Set oRng = oSource.Range
With oRng.Find
Do While .Execute(findText:="the supplier")
oRng.Start = oRng.Sentences(1).Start
oRng.End = oRng.Sentences(1).End
Set oTargetRng = oTarget.Range
oTargetRng.Collapse 0
oTargetRng.FormattedText = oRng.FormattedText
oRng.Collapse 0
Loop
End With
Set oRng = Nothing
Set oTargetRng = Nothing
Set oSource = Nothing
Set oTarget = Nothing
End Sub