Timer- To Write Code Which Takes A Reading Off Of A Device Every .005 Seconds

I am trying to write code which takes a reading off of a device every .005 seconds.

When I write the code as follows to take the reading every .004 seconds things work well.

PauseTime=5
Start = Timer
Oldtime=Timer
Do While Timer < Start + PauseTime
If Timer > Oldtime + .004 Then
Oldtime = Timer
Read(count) = Orbit.Networks(0).Modules(0).ReadCurrent
count = count + 1
End If
Loop
Finish = Timer

If however in the above code I only change .004 to .005 instead of taking readings every .005 seconds, I end up with readings roughly .015 seconds apart (approx)

Is there something unstable about the timer function to do this? Is there a different way to get a more stable result?