For Macintosh, GeneJockeyII does this.
It's a major sequence handling package though, and costs.
Call Biosoft
US : (314)524 8029
UK : (0)1223 68622
Interest declared : I wrote it!
Phil Taylor | MRC Reproductive Biology Unit
| Centre for Reproductive Biology
| 37 Chalmers Street
mbplt at seqnet.dl.ac.uk | Edinburgh EH3 9EW
ptaylor at hgmp.mrc.ac.uk | Scotland.