How to restrict data input.

[Yodo]

I have several columns that should have "+" or "-". Users correct these columns and sometimes they put double "++" or "--". How to lock column to store only "-" or "+" and nothing else?

[alansidman]

Set the length of the field in the table design to 1.

[Homegrownandy]

you could also do some validation in VBA for the textbox where this data is entered.

[Yodo]

Thank you! The first approach is the simplest one, so I stick to it. Users will not confuse plus or minus with a letter or a number.