Works in Delphi....

[james]

This doesn't work in Lazarus.  Am I missing maybe needing to add a unit?

procedure TForm3.Edit2Change(Sender: TObject);
begin
 (this part here -->) if Key in ['0'..'9','A'..'Z','a'..'z'] then
 begin
 Exit;
 end else
ShowMessage('You may use ONLY a combination of: a-z, A-Z, 0-9')
Key:=#0;
end;   

[typo]

Because "Key" is unknown. You need to put this on an OnKey event handler where Key is a parameter.

[james]

Thanks. 

OnKeyPress to be exact.