I done word file splitting in below coding
objdoc = objapp.Documents.Open(obj, missing, oFals, oTru)
range = objapp.ActiveDocument.Range
range.Find.ClearFormatting()
range.Find.Replacement.ClearFormatting()
range.Find.Execute(regobj, missing, missing, oTru, missing, missing, oTru)
Do While rang.Find.Found
range.Select()
matchcollection = Regex.Matches(tet, "^\[ITS_(.+?)\]")
objapp.Selection.Cut()
objdoc.SaveAs()
objdoc.Close()
objapp = CreateObject("word.Application")
objapp.Visible = False
objdoc = objapp.Documents.Add
objapp.Selection.Paste()
objdoc.SaveAs(obj1, obj2)
objdoc.Close()
Loop