Custom Format Point Labels

I am trying to format PART of a string on a point label.  I don't know the syntax to bold, underline, etc to use in an expression.  In the attached code I would like to Bold or maybe use a different color font on ONLY PART (the part after "  ")  OF THE equation.  I know how to apply it to the whole thing.

=(Fields!Sales_Rep.Value & "  " & FormatPercent(Fields!Total.Value/Fields!Goal_to_Date.Value,0)) & " of Goal"

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