Такой макрос может вам помочь. Извините за форматирование.
Sub HTMLConvert()
Dim X As Integer
Dim Y As Integer
'Make your range of rows here
For X = 1 To 50
'Make your range of columns here
For Y = 1 To 10
'Each tag that you want to look for needs one of these if statements
If InStr(1, Cells(X, 1), "<b>") > 0 Then
'Keep in mind this solution will only bold the whole cell, not part of one.
Cells(X, 1).Font.Bold = True
Cells(X, 1) = Replace(Cells(X, 1), "<b>", "")
'If you have a closing tag, like </b>, make sure you clear it too
End If
Next
Next
End Sub