I want to represent a set of sequences that occur within CDS regions of genes and then load these as UCSC tracks to browser. I need to fetch the CDS sequence of a gene, see where my sequences of interest lie, and then output that as a format loadable in a track in UCSC. What is the right format for this? It would need to represent spliced alignments since CDS coordinates are different from the genomic coordinates. Is there an easy and flexible format to keep all necessary info in?