You can try this, in the OnFormat event of the section where the fields are
located, add the code
If Len(Me.[Student Name] & Me.[Student Surname]) > 19 Then
Me.[Join FieldName].FontSize = 8
Else
Me.[Join FieldName].FontSize = 12
End If

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BS"D
> I have a field in a report of =[Student Name] & " " & [Student Surname] I
> want to say that if there are more than 20 characters in that text box then
[quoted text clipped - 3 lines]
>
> thanks so much!