How can I auto tile my texture along the X-axis

I am building a procedural landscape. The landscape will be 100 on the Y and an unspecified amount on the X (But X will be divisible by 100 and much bigger than Y). I want the material to cover a 100 by 100 area on the landscape and then tile along X when I increase X

how can I do this?

A quick drawing that explains this: Imgur: The magic of the Internet