never seen a VDP caluclated that way before....If its for Time, take 10% of your HAT. say your HAT is 400'. Thats 40 Seconds. If your Time for the approach is 3:40...you will arrive at your VDP at 3 minutes. (40 seconds priopr to the missed approach point)

If its based on DME, devide your HAT by 300. Say your HAT is 300'. You're doing a LOC/DME approach. Missed is at 1.5 DME. 300/300=1. Add 1 mile to your missed DME to get your VDP....2.5DME you will be at the VDP(1 mile prior to the Missed approach point). You will need to either add or subract the DME figure you get depending on whether the navaid you are using is on the field or off the field. If it is on the field, such as in my example, you add to your Missed DME to get the VDP if its off the field, you subtract it.