Photoshop Blending Options Help Please!!!?

I have got a plain black square and when i click blending options i want it to have a gradient so I select the gradient and that is all ok but I also want a pattern over the top of it which is some scan lines but it won't do it. If not how do you manually make the square have a gradient so then I can go to blending options and put a scan line pattern on top of it ??