A drill guide assembly (10) for a drilling tool (50) having a chuck engaging a bit portion (54) comprising a tip (62) and a length extending from the chuck, the drill guide assembly comprising a first member (14), a second member (12) and a trackable member (16). The first member (14) is adapted to abut a workpiece surface and defines a central aperture (19) therethrough adapted to receive the bit portion. The second member (12) is adapted to be axially displaced with respect to the first member and is axially biased therefrom, and defines a central aperture (11) therethrough adapted to receive the bit portion. The trackable member (16), fastened to the second member, comprises a detectable element (35) adapted to be located and tracked in three dimensional space, thereby defining the position and movement of the second member and therefore that of the drilling tool bit portion.