Help with writing a Formula

I'm thinking I can use a 'formula' field to do this task. Can anyone help with the 'Formula' field... or is there a better suggestion. Thx.

IF
First 4 characters of a record in {Unit & Week} = First 4 characters of a record in {Unit Name} AND {2023 Fee Paid} is Checked, insert the amount in {2023 Maint. Fees} field.

Association Table
{Unit & Week} is not the primary field
{2023 Fee Paid} is a Checkbox

Maint Fees Table
{Unit Name}
{2023 Maint. Fees}