Hey so one of my models is a brick wall which i have used "UVW map" modifier on it to make the bricks the right size by tiling the texture and ive got another texture of dirt added onto the material of the wall using mix, it look like this (http://i.imgur.com/d7GgilH.png), however i dont want the dirt to be tiled becuase it looks like this (http://i.imgur.com/dNePBds.png) is there a way to have the brick texture tiled without having the dirt tiled?

P.S I tried having the dirt on another plane model and moving it just before the wall but that causes clipping issues and you can see it floating off the wall.

That's what different UV channels are for. Each vertex can have a different UVW coordinate in each channel, and you specify what channel a texture will use.

In 3ds max you control that with a spinner in the modifier rollout:

http://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/3DSMax/files/GUID-78327298-4741-470C-848D-4C3618B18FCA-htm.html

So you will map your brick wall twice: set the channel to 1 and map it with tiling (use the tiling from the UVW map modifier, not in the material settings). Then collapse the modifiers, add a UVW map modifier, set the channel to 2 and map it in the entire wall.

Set the brick texture to UV channel 1 and dirt texture to UV channel 2. You set this in the Coordinates rollout of the bitmap material.

You can also set this back in your game engine.