[galaxy-dev] outputting different numbers of files based on variables?

Hi all, Is it possible to output a different number of files based on variables that the use has chosen? I have a program that will output different numbers of files based upon the input data. So, for example, if the user wants to use a single-end fastq file, the program outputs only one file, however, if the user chooses paired-end fastq files, it outputs three files. Is there any way to get that to work in just one tool? I could make separate tools for single vs. paired end, but I'd rather not. - Nik.