updating a column based on info from another coluimn? Desperate!

Hi All, This is OT but I am in need of serious help. I am rewriting URL's for a site and came across an issue with spaces in URLS having %20 applied to them. I can't seem to find a solution with mod_rewrite to get rid of the %20 and replace with - (hyphen) so I am hoping someone can help me here with an MySQL solution. I have over 4000 records in a table. I've added a new column in that table called newUrl Is it possible with a QUERY to take from the 'designers' column and write into the 'newUrl' column and replace spaces with - at the same time? I'm probably talking out my a$$ here but I am a little desperate for a solutions. Thanks in advance and again my apologies for the OT message. Aaron