Ok there is one way to do this hopfully I can make it clear and you have the programs.
First the admin must have Infopath. Create a new form with the following data fields
- Date payment received
- Payment no.
- Payee
- Currency
- Amount
Publish it to a sharepoint form libary.
In the form libary add a column for "Who is reponsible"
Go to permissions and make user only able to edit items, (Remove the ability to add items, and remove manage views)
Got to views and within each view remove all execpt for the above fields and who.
Create a default view of datasheet view and again make sure to only have the above fields.
Now that this does is that the admin will have the infopath form and can add items to the list. When the items are displayed in the list users will not be able to change the contents of the cell, (only way to do that is to open the infopath form which they will not have installed on their computer or you remove the links from the views) And have the one added field of "Who" the user will be able to change it from the datasheet view.
This is not a fullproof solution but its the closest I can get. It took me about 1/2 hour to setup on a test machine.
Good Luck
Brian