Macro to convert specific text and format specific text within a string

Different method

Option Explicit

Sub test()
    Dim r As Range, temp, num
    Const div As Double = 22.046
    With CreateObject("VBScript.RegExp")
        For Each r In Range("a1", Range("a" & Rows.Count).End(xlUp))
            If r.Value Like "*USD/MT" Then
                r.Value = Replace(r.Value, "USD/MT", "USC/LB")
                .Pattern = "(\+|\-)(\d+(\.\d+))"
                If .test(r.Value) Then
                    num = Format$(Round(CDbl(.Execute(r.Value)(0).submatches(1)) / div, 2), "#.0000")
                    r.Value = .Replace(r.Value, .Execute(r.Value)(0).submatches(0) & num)
                    r.Characters(1, 2).Font.Bold = True
                    r.Characters(.Execute(r.Value)(0).firstindex + 2, _
                    .Execute(r.Value)(0).Length - 1).Font.Color = vbRed
                End If
                .Pattern = "USC/LB"
                r.Characters(.Execute(r.Value)(0).firstindex + 1, .Execute(r.Value)(0).Length).Font.Bold = True
            End If
        Next
    End With
End Sub