This looks like a homework assignment but in any case this forum is not a free code writing service. If you want to learn VBA, there are plenty of people here willing to help. To get you started:
Sub ScratchMacro()
'A basic Word macro coded by Greg Maxey
Dim oRng As Range
Set oRng = ActiveDocument.Range
With oRng.Find
.Text = "<[AEIOUaeiou]*>"
.MatchWildcards = True
While .Execute
oRng.Characters.First.HighlightColorIndex = wdYellow
oRng.Collapse wdCollapseEnd
Wend
End With
lbl_Exit:
Exit Sub
End Sub