Having partial text in a cell change to bold.

ScottF1870 

The following will on;y work in the desktop version of Excel for Windows or Mac.

Press Alt+F11 to activate the Visual Basic Editor.

Select Insert > Module.

Copy the following code into the new module:

Sub BoldAfterMM()
    Dim c As Range
    Dim p As Long
    Application.ScreenUpdating = False
    For Each c In Range(Cell1:=Range("A2"), Cell2:=Range("A2").End(xlDown))
        p = InStr(c.Value, "MM")
        If p > 0 Then
            c.Characters(Start:=p + 2, Length:=1000).Font.Bold = True
        End If
    Next c
    Application.ScreenUpdating = True
End Sub

With the insertion point anywhere in the code, press F5 to execute it.

Switch back to Excel.

If you want to be able to run the macro again later on, save the workbook as a macro-enabled workbook (*.xlsm) and make sure that you allow macros when you open it.