[NTG-context] How to know the text was to big

I want to create a pdf-document which has severall frames in which user supplied data has to be put. I have two questions about this: - How can I use parameters to fill the boxes? - When one or more of the supplied texts does not fit its frame the pdf document is 'corrupt'. How can I see that at least one of the texts did not fit its frame? -- Cecil Westerhof