Send a list of id's to web url as a query string using VB.NET

My code is crap. I have a list of over a 1000 ID numbers that I need to break up into smaller segments to send to a web api. I can only send less than 200 at a time and I can only do 3 requests in a second. The attached file has my code but I'm only interested in breaking up the url using VB.NET. I've had other people do this before and some of them worked and some were crap. If you have a CLEAN way to do this I'm interested.