Hey,
There is only one way to do what you want, and still get your commission.
What you need is to drop the cookie on your visitor. This means the visitor is recognized as coming from you, and you can then send them to the vendor's landing page, or salespage, and still get credited as the referring affiliate.
That is the way to do what you are asking, but, sadly, it's a complex thing to do.
For two reasons:
1. Some vendors only recognise the last cookie dropped so if the vendor's landing page also drops a cookie, you'll lose the credit, unless you route straight to the order page, and
2. Dropping a cookie can be considered as cookie stu**ing. That's a BH technique, and all discussion about is banned on many forums, so it's not easy to find the appropriate scripts or threads nowadays, even if you want to use it for whitehat reasons.