How to confirm the vertex of a mesh that mouse in and change its texture

Hello, everyone. How to confirm the vertex of a mesh that mouse in and change its texture, i wanna to draw a hallway with mesh dynamicly and there will be some bombs in the hallway, when the bomb explode, i wanna to get its position and simulate the explision by changing the hallway's texture at where the bomb explode.The first problem i come across is how to get the vertext and map another texture on it. Or is there another way to simulate this effect? thanks a lot!