Need Excel expert immediately for small Data Validation project

I am in need of an Excel expert who can assist me with a small data validation project. The ideal freelancer should have experience in data validation and be able to create custom formulas to prevent errors. Some additional details about the project include:

- The type of data validation needed is both a dropdown list and a custom formula that prevents data entry based on values in other cells
- I require assistance with creating the custom formula.

I will likely need additional help with more custom formulas as this project progresses