I think your problem may be that the 128 is a number and may need to be a string based on the field. You are using DefaultAttribute so if the default resolves to a string then the "then" portion of your If statement must be string also.

Now, the DefaultAttribute is usually found when you are doing conditional formatting like changing fonts based on the values of a field, etc. So if you are changing from Regular to Bold, then the default may be Regular which is a string. So maybe if the words DefaultAttribute are not in the Functions area of the Formula Workshop then you may need to find something else for the Else.

Hope this helps