[VBA] Activate a dgnlib textstyle

How to activate textstyle programmatically(like after key-in:textstyle active "Tahoma_03_LT") which is from attached library(TextStyle.IsFromLibrary )?

   Dim txsp As TextStyle

Set txst = ActiveDesignFile.TextStyles.Add(Nothing, "Tahoma_03_LT")
        Set txst = ActiveDesignFile.TextStyles.Find("Tahoma_03_LT")

txsp.UsesColor = False

This gives "unknown error". If comment out "Set txst = ActiveDesignFile.TextStyles.Add(Nothing, "Tahoma_03_LT")" then I get "run-time error 2147221504 (80040000):  The TextStyle is locked and cannot be modified." which is not a surprise as  textstyle in dgnlib can't be modified. I need to change usescolor flag as workaround to Defect 668134.