Does anyone have a lay only betting spreadsheet, where you can adjust the commission and stake please?

I've run into trouble and searched everywhere, but there's only back and lay type spreadsheets.

Here's what I've got so far:
J4 = Stake
J5 = Commission
I7 = Either blank (horse did not win) or BFSP odds (horse won)

Current formula is =IF(I7="",$J$4*(100%-$J$5),(-I7-$J$4)+$J$4*2)
Works fine on 7% commission and $1 stake

BUT if I change either the stake or commission% everything goes haywire.

Any help or suggestions gratefully accepted!

__________________
RaceCensus - powerful system testing software.
Now with over 407,000 Metropolitan, Provincial and Country races!
http://www.propun.com.au/horse_raci...ng_systems.html
*RaceCensus now updated to 30/09/2024
Video overview of RaceCensus here:
http://www.youtube.com/watch?v=W821YP_b0Pg