The Prince of Wales' charity is to get £1.6m from the Live 8 concert in London's Hyde Park after cancelling its own pop show to make way for the event.
The Prince's Trust agreed to scrap its annual Party in the Park, which was scheduled for 2 July, when plans for a new Live Aid concert got under way.
The money will come from text messages sent in the competition to win tickets.
U2, REM, Madonna and Coldplay will play in Hyde Park to raise pressure on world leaders to fight poverty in Africa.
Text lines are expected to be inundated when the competition opens on Monday.
It will be the only way for the public to get hold of the 145,000 tickets, with each entry costing £1.50 plus the normal text rate.
The Prince and Princess of Wales were at the first Live Aid in 1985
The event is not primarily designed to raise money, but the first £1.6m from text messages will go to The Prince's Trust, which was set up by Prince Charles in 1976 to help young people in the UK.
Money will also go to Help a London Child, the charity run by radio station 95.8 Capital FM.
Capital FM, which broadcasts Party in the Park, will also be the commercial radio partner for Live 8.
A statement from The Prince's Trust said: "During talks with Bob Geldof and the Band Aid Foundation, The Prince's Trust and Capital Radio were happy to cancel this year's Party in the Park to support Live 8.
"Mr Geldof and his team were anxious that disadvantaged young people in the UK did not suffer as a result and offered to give The Trust and Help a London Child money from the ticket ballot."
Prince's Trust chief executive Martina Milburn added: "Thanks go to Bob Geldof and his team for their generosity and support of our work with disadvantaged young people."
A multiple choice competition question will be revealed on Monday, along with a text number to send entries to. Lines will be open until midnight on 12 June.
Any extra money raised by the text messages will go towards the cost of staging the event.
Dido, Sir Elton John, Keane, Mariah Carey, Scissor Sisters, Sir Paul McCartney and Sting are among the other stars who will perform in Hyde Park.
Stevie Wonder, 50 Cent, Bon Jovi and Maroon 5 will play at the US leg in Philadelphia.
Other gigs in Paris, Berlin and Rome are also feature local and international stars.
The events will take place days before world leaders gather for the G8 summit in Gleneagles, Scotland.
Geldof hopes Live 8 will generate enough pressure to "tilt the world on its axis" to improve debt payments, aid and trade for African countries.
The Glastonbury festival has joined the Make Poverty History campaign, with a plan for all 112,000 fans at the event to join hands to show their support.
The "gesture of solidarity" will form a human line through the site at 1600 BST on Saturday 25 June, festival organisers said.