If you place a column name in brackets, and it is not an actual column in the table, it would prompt for a parameter.

Are the [Date], [Day] columns actual columns?

I am not sure what you are exactly trying to update, but it looks like you are trying to update a date column with a new format which includes the month name.

There are way, way better days to format date strings that having to go through all that..

1. Is the [Date] column an actual datetime datatype? or is it a string?

2. Givent the built in flexibility of being able to manipulate the format of datetime data types, it doesn't seem practical to update the field in this way (or to have separate columns for [Day] if that is the case.

3. What is the datatype of the [Date] column, what is sample value from that column, and what is the desired result of your update?

I am assuming somewhere in the code you are establish a connection with with do be allowed to run DoCmd..

With CurrentDb for example in Access vba.

If from a VB program, you would need to set the connection string as well.