Alison Sharland, 47, agreed a £10.35million settlement in a deal that saw her give up her claim to an equal share in her husband's software company.
But husband Charlie had lied about the value of his share in AppSense, and she now says she is entitled to more.
The Court of Appeal found that Mr Sharland, 54, had deliberately hidden information and lied to the court but refused to overturn the divorce settlement.
Mrs Sharland will now take her fight to the Supreme Court.
The Sharlands, from Wilmslow in Cheshire, married in 1993 and Mr Sharland founded the software company AppSense in 1999.
The couple, who have three children, separated in 2010 and agreed to split their assets.
But they could not agree over the value of Mr Sharland's share of AppSense, which has grown to become one of the biggest firms of its kind in the world with offices in Silicon Valley, New York, Australia and across Europe.
She eventually agreed to accept £10.35million in cash and property and 30 per cent of the proceeds from her husband's shares when they were put on the market.
The deal was agreed on the basis that they were worth no more than £32million.
But within days of the agreement an initial public offering on the stock market – which never took place – valued the company at more than £460million, meaning his shares were worth around £132million after tax.
Mr Sharland did not dispute that he misled his ex-wife and an Appeal Court judge said his conduct was 'deliberate and dishonest' but the court ruled that Mrs Sharland was bound by the agreement she had signed and refused her appeal.
The case will now be heard at the Supreme Court in June.