[galaxy-dev] <param> multiple formats

Hi, is it possible for a input parameter to accept multiple format types (e.g csfasta and fast), or do I need to write two separate tool configs? For example if I have a format conversion tool which accepts a number of input formats and converts them to a specific output format do I need to write a tool config for each conversion? One way around this would be to include a conditional in the tool config and let the user specify the input type, but is there another way (preferably not involving writing large conditionals)? Cheers Dominic