[NTG-context] How to get the number of lines of a paragraph?

Dear all, I need to draw underlines under a paragraph. The number of underlines is determined by the number of lines of the paragraph. For example: If the paragraph have one line: text of paragraph, blur blur. ---------------------------------------------------------- If the paragraph have two lines: text of paragraph, blur blur blur blur blur blur blur blur ---------------------------------------------------------- blur blur blur blur blur blur blur blur. ---------------------------------------------------------- Another question: How can I set the header of the pages of contents? Thanks! Best wishes, Wei-Wei