Formula for distributing cashflow accurately over months using specific dates

Hi,

I am hoping someone can help me out here!

I have a forecasting sheet where I have a campaign that starts and ends on specific dates. It then feeds into a larger overview spreadsheet in just monthly form. What I need to do is have it shared appropriately between the months.

For example:

A campaign starts on 15th February and the end date is 23rd of April. The income from this is £20,000. Thus we have 67 days. However the spread of income over Feb, Mar and Apr is 4179, 9254 and 6866.

What is the formula to get this though!?!?

Thanks