A somewhat equivalent technique to use with Navigator 4.x is a combination of document.write and document.close. However, this will only work with layer type objectsobjects defined using the LAYER tag (don't use this), or content contained in positioned DIV or SPAN blocks. To replace contents, use something similar to this code (if you've attached an identifier of "test" to the block):
Navigator creates a new document object for each layer, and document supports the write method to create the document's contents. The close method then forces a redraw. One area where innerHTML and document.write differ is that document.write does not preserve any CSS styling for the block.