UDF to replace characters in free text?

Hi experts,

If I have dates such as "2009.11.12" in a free text I need to change those to "2009-11-12".

Basically I have to replace dots with a hyphen.

I am thinking of a UDF but could not find one in the forum. Does anyone have an idea how to achieve that?

Thank you very much for your help!

Best regards,

Peter