using "set criteria" in lookup

using "set criteria" in lookup

Him

I have two forms one with the columns (Event, Number, Name....) and one with unique entries (Number, Name).
  
In the first I'd like to lookup the "Name" from the second form when the "Number" columns are the same. There should be only one match in the second form.

I don;t know how to set the criteria to do so. Is there some guide on this?

e.g. if I enter the following in the second form

Form2
Number,Name
1001,Joe
1002,Jim

then if an entry is added to form2 for Number=1001 then the Name should be Joe
e.g.

Form1
Event,Number,Name
1,1001,Joe
2,1001,Joe
3,1002,Jim
4,1001,Joe



thanks for any help