Betting formula

Hi all,
I'm trying to create a spreadsheet for placing two bets - one at a bookie and one at an exchange which leave equal profit or loss.
Basiclaly - I need to fill a cell with a number which will cause my two profits at the bookies and exchange to be as close to equal as possible.
Here is an example.

Place £10 at Ladbrokes on Man U to win at odds of 2.0 meaning either £10 loss or £10 win
At Betfair I need to place a lay bet of ?? in order to cover the 5% commission and leave me with as nearer profit or loss to the bookies.
i.e if I placed a lay bet of £10 at Betfair if the bookies won I would end £0 profit/loss while if Betfair won I would end up -50p due to the comm, I need a formula which will give the lay figure to ensure both these numbers were as close as possible - in this case a lay of £10.26 would leave me with a -25p at both bookies - but how do I get the spreadsheet to work out this £10.26 figure for me?
Sorry for the long message!!

Does this look right?

      ---A--- -B-- ---C--- ----D----- -----E-----
  1    Type   Comm   Bet   Horse Wins Horse Loses
  2   Win Bet   0% 100.00     100.00     (100.00)
  3   Lay Bet   5% 102.44    (102.44)      97.56 
  4                            (2.44)      (2.44)

The formula in C3 is =C2 * (1 + B3) / (2 + B3) * (2 + B2) / (1 + B2)

It's the commissions on the win bet and lay bet respectively. So if there's a $100 bet, it costs $105 if there's a 5% commission. Or for the example in the table, you have to put up 102.44 to get 102.44/(1.05) = 97.56 on the table.

It doesn't consider odds because I don't understand your odds. It seems to me if you arrive with $10 in your pocket and place it at 2:1 odds (and no commission), you walk away with either $30 or $0, not $20 or $0. My table assumes what I would call 1:1 odds.

If you explain how they work, I'll add odds. I assume that they would, in general, not be the same for the Win and Lay bets?

So if Man O' War were racing a horse with a wooden leg in a two-horse race, what would the odds be on Man O' War?

Whaddaya mean, which cells are which? I thought they were pretty clearly labeled.

The formula in the box is my derivation of the formula used in the worksheet to compute the lay bet amount.

       ---------A--------- --B--- ---------------------------C---------------------------
   1   Stake (Bookie Bet)   10.00 B1: Input                                              
   2   Back odds             4.00 B2: Input                                              
   3   Exchange (Lay) odds   4.30 B3: Input                                              
   4   Exchange (Lay) Comm     3% B4: Input                                              
   5   Bookie Comm             0% B5: Input                                              
   6                                                                                     
   7   Bookie win           30.00 B7: = B1 * (B2-1)                                      
   8   Bookie lose         -10.00 B8: = -B1                                              
   9                                                                                     
  10   Exchange win          9.09 B10: = B13 * (1 - B4)                                  
  11   Exchange lose       -30.92 B11: = B13 * (1 - B3)                                  
  12                                                                                     
  13   Lay figure            9.37 B13: =ROUND( B1 * ( (B2-1) * (1-B5) + 1 ) / (B3-B4), 2)
  14                                                                                     
  15   Profit                                                                            
  16   Bookie win           -0.92 B16: = B7 + B11                                        
  17   Exchange win         -0.91 B17: = B10 + B8

Nuovo Foglio di lavoro di Microsoft Excel modificato.xlsx
hello guys I have a question:
I would like to develop an excel spreadsheet where I'm from automatically setting the formula, the amount to bet on the second book, in order to have a fair win on both bookmakers. Keep in mind that the sign I tip 35% of the net profit.
I am attaching the file that I did, but I manually set the value of the sign back.
thank you

orgagigio,
Unfortunately your post does not comply with Rule 2 of our Forum RULES. Do not post a question in the thread of another member -- start your own thread.

If you feel an existing thread is particularly relevant to your need, provide a link to the other thread in your new thread.

Old threads are often only monitored by the original participants. New threads not only open you up to all possible participants again, they typically get faster response, too.

There's an updated version of the workbook, with both Dutching and Lay Betting, at https://app.box.com/s/5pt3sgepeuoj8q42lp36