The OnRenderEnd script is executed after rendering of the item (which might be a section, band or component). This script allows post-processing of the render result. As the render result may vary based on the data input, it is advisable to use OnRenderBegin where possible, rather than OnRenderEnd. For example a field may output zero, one or more Text elements depending on the input data - you shouldn't assume you will always get one Text result out.
-- JonPriddey - 04 Aug 2005