You can record a macro that will do that. e.g.
Code:
Sub Macro1()
Selection.HomeKey wdStory
Selection.Find.ClearFormatting
Selection.Find.Replacement.ClearFormatting
With Selection.Find
.Text = "***"
.Wrap = wdFindStop
.Format = False
.MatchCase = False
.MatchWholeWord = False
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
End With
Selection.Find.Execute
End Sub
It might make more sense to replace your asterisks with content controls e.g.
Code:
Sub Macro2()
Dim oRng As Range
Dim oCC As ContentControl
Dim i As Integer: i = 0
Set oRng = ActiveDocument.Range
With oRng.Find
.Wrap = wdFindContinue
Do While .Execute("***")
i = i + 1
oRng.Text = ""
Set oCC = oRng.ContentControls.Add(wdContentControlRichText)
oCC.Title = "Text" & i
oCC.Tag = oCC.Title
oCC.LockContentControl = True
oRng.End = oRng.End + 1
oRng.Collapse 0
Loop
End With
End Sub