how to find/replace part of the url

[yazan]

Hello,
i need to to add a suffix in the end of a specified url, each time it's being loaded..
for example i want http://google.com/q=hello
to be http://google.com/q=hello&c=1
adding "&c=1" at the end
or
simply replace any url containing "q=hello" to "q=hello&c=1"
thanks in advance.