Your macro isn't far off being correct. Try:
Code:
Sub ListChange()
Application.ScreenUpdating = False
Dim MyList() As String, i As Long
Options.DefaultHighlightColorIndex = wdYellow
MyList = Split("additionally,ah,almost,big,can be,could,could be,generally speaking,he,in,it,it is,low,many,may,might,most,plenty,she,should,some, these,they,this is,we,with", ",")
With ActiveDocument.Range.Find
.ClearFormatting
.Replacement.ClearFormatting
.Replacement.Highlight = True
.Replacement.Text = "^&"
.MatchWholeWord = True
For i = 0 To UBound(MyList())
.Text = MyList(i)
.Execute Replace:=wdReplaceAll
Next
End With
Application.ScreenUpdating = True
End Sub
Do note that you'll also get word forms ending with 's highlighted, but the 's won't be highlighted.