If you need to update a URL field in a links list (or any other list) from SharePoint Designer, you need to know this little trick. Create a string that contains the URL and description like this:
URL, Description
and then update the field with this string. Notice there is a comma AND A SPACE after the URL. There are no brackets, curly braces or octothorpes (# signs) involved in the string.
Using the string builder, you can see the "input" and the "output" of the workflow.
Are you a user? 
I’m using the same solution with a workflow. The only problem i am getting is the following :
– If the value of the webaddress has a comma than the description field is updated in a wrong way.
URL : http://server/Lists/Clients/EditForm.aspx?Company=Company, Ltd
Desciption : Ltd, View
The right description should be : View.
But the comma in the URL is used.
How can i find a way to prevent the description from changing into the wrong value ?
Regards,
RdJ
URL encode the comma with %2C?
?Company=Company%2C%20Ltd
Worth a try.
Thanks for this simple but helpful post. Solved my problem.
Can this be used with a local variable in the URL string?
Yes, I believe so.
thank you very much for this tip
Excellent… Thanks for the post. That space between a comma and title field was really worth mentioning. Well done!!
Thank you your post was really helpful to me! Bless you!