Case insensitive pattern matching

Hi,

I am trying to validate using regular expressions but I dont want it to be
case sensitive.

e.g

<xsd:pattern value="NOW ?[+-] ?\d ?HOUR(S)?"/>

I could make it work by doing something like,

<xsd:pattern value="[Nn][Oo][Ww] ?[+-] ?\d ?[Hh][Oo][Uu][Rr]([Ss])?"/>

But it quickly becomes painful and hard to read.

Is there any switch to turn off case sensitivity?

Regards,

Mark