[NTG-context] counting characters when dealing with XML

Dear list, I have a question when dealing with XML. Is there any way to write a conditional based on the number of characters in a given field? I mean, the following field: \xmltext{#1}{h1[@class='subtitle']} If subtitle > 60 chars, then fontsize = 10pt. If subtitle > 50 chars, then fontsize = 12pt. If subtitle > 40 chars, then fontsize = 14pt. If subtitle > 30 chars, then fontsize = 16pt. How could I write these conditionals? Many thanks for your help, Pablo -- http://www.ousia.tk