On the selected measures screen you can split a single measure between multiple funding sources by first clicking the notepad icon.
Click the button to assign the first funding source. Enter the quantity or amount (under Total Cost) you want assigned to the first funding source. Save
Click the button again to add the next funding source.
Select the next funding source and the remaining quantity or amount will autofill. Save
Learn more about what the Selected Measures screen can do for you by reading this article.