Assuming you're trying to build a WHERE clause, you can't use Or like that.
You need either:
[Category number] = "111" OR [Category number] = "222" OR [Category
number] = "333"
or
[Category number] IN ("111", "222", "333")

Signature
Doug Steele, Microsoft Access MVP
http://I.Am/DougSteele
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>I made a form that allows the user generate a report based off the category
> that they pick. When they choose a category, the category number pops up.
[quoted text clipped - 7 lines]
> If Category = "hat" Then
> Category number= "111" OR "222" OR "333"