A family of Microsoft relational database management systems designed for ease of use.
I just want to add a voice in support of the solid, professional advice Daniel and Ken have provided. They are two of the most reliable, experienced and widely respected experts on Access development participating here. There are, of course, others here who are in that same category.
Over the years, Microsoft has often injected interface design elements, such as Lookup Fields and Input Masks, into data elements, despite the fact that doing so muddies the waters unnecessarily.
Their justification for doing so, is that it "makes it easier" for beginners to get started. However, beginners are the very people who don't yet understand the negative implications of forcing interface design features into the wrong objects, i.e. tables. Hence, they can get off on the wrong foot and end up in difficulties such as the problem expressed in this discussion.