Offset / hedge calculation - formula or spreadsheet?

[jaipal2004]

Hi,

is there a spreadsheet available that allows me to enter he BSP odds, a % offset for a lay bet and determine the return if I hedged at the % offset?

Or some kind of formula?

ie. I want to know what the lay odds and hedge amount would be if I backed a horse at odds of 10.5 with 50% offset

thanks