ERROR while using HTTP_GET FUNCTION MOUDLE

Hi frnds,

Need your help in sloving the requirement..

In t.code iw21 for PM(notifictaions) while we enter using the M2 r m5. It opens the creation of notification there at the end we are adding a button .

when ever the button is clicked it should open the Browser(Url)

So we are using HTTP_GET Function module while the button is clicked  the url should be populated.

But here it was showing the error when we click on the button .

Do we have any other alternative standard function module to pass the url which is similar to HTTP_GET..