Decimal points in %series-part%

[Truk-22]

I like to have my files named with ['['%series% %series-part%']'] first. However when there are books in the series that are not full integers, it will look like [series 1.5]. Full integers would look like [series 1]. When windows sorts this, it would but [series 1.5] first. Would anyone have an idea of how to structure it so full integers add a .0, for example [series 1.0]?

Many thanks in advance