odds question

Im looking for a spread*** that can sort out the following
calculation

In a two horse race I bet on horse 1 at start of race say £20 at a
fixed odds,

Then as the odds change during the live race I can back or lay either
horse, is there a spread*** that will give me the optimum cash
inputs during the race to give me the best possible outcome, ie
minimise a possible loss or increase a potential win.

.