Try something like:

Sub FormatBetweenTags()
Dim startTag As String
Dim endTag As String
Dim x As Integer
Dim y As Integer

startTag:
startTag = InputBox("Enter the start tag (e.g., < )", "Start Tag")
If Len(startTag) < 1 Then
 If MsgBox("You did not enter a start tag. Please press OK to go back" _
    & " and enter a start tag or press CANCEL to exit.", vbOK +
vbExclamation, _
    "Invalid Entry") = vbOK Then
   GoTo startTag
 Else
   Exit Sub
 End If
End If
x = Len(startTag) - 1
endTag:
endTag = InputBox("Enter the end tag (e.g., & > )", "End Tag")
If Len(endTag) < 1 Then
 If MsgBox("You did not enter an end tag. Please press OK to go back" _
    & " and enter a end tag or press CANCEL to exit.", vbOK +
vbExclamation, _
    "Invalid Entry") = vbOK Then
   GoTo endTag
 Else
   Exit Sub
 End If
End If
y = Len(endTag) - 1
FormatBetweenTags startTag, endTag, x, y
'FormatIncludingTags startTag, endTag
End Sub
Sub FormatBetweenTags(startTag$, endTag$, x As Integer, y As Integer)

Dim oRng As Range
Dim myRange As Range
Dim i As Long

Resetsearch

Set oRng = ActiveDocument.Range
ActiveDocument.Range(0, 0).Select
With oRng.Find
 .Text = startTag$
 .Wrap = wdFindStop
 While .Execute
   i = oRng.End
   oRng.Collapse direction:=wdCollapseEnd
   .Text = endTag$
   If .Execute Then
     Set myRange = oRng.Duplicate
     myRange.Start = i - x
     myRange.End = oRng.Start + y
     myRange.Font.Italic = True
     .Text = startTag$
     oRng.Collapse direction:=wdCollapseEnd
     oRng.Select
     End If
  Wend
End With
End Sub
Sub Resetsearch()
With Selection.Find
  .ClearFormatting
  .Replacement.ClearFormatting
  .Text = ""
  .Replacement.Text = ""
  .Forward = True
  .Wrap = wdFindContinue
  .Format = False
  .MatchCase = False
  .MatchWholeWord = False
  .MatchWildcards = False
  .MatchSoundsLike = False
  .MatchAllWordForms = False
  .Execute
End With
End Sub