Thanks for the nodes lesson ha, im not simply wanting to blend the two. the white circle is being used as a mask at this stage as thats the only area i want to be affected. within that area of the mask i need to create a varibale that can be manipulated in BP and used as a dynamic material instance. that variable needs to display a number of dots (variable) on any desired UV space within that mask. Maybe ive gone the complete wrong way of doing this but i’d didnt really have a great idea on how to start. the mask represents an area on a mesh in which i want to create a radar.
Hope ive made it clearer what i want 
Thanks