[lmikle]

Код:

var
  I : Integer;
  A : Array Of Integer;
begin
  Case ComboBox1.ItemIndex Of
    0  : SetLength(A,3);
    1 : SetLength(A,10);
    2 : SetLength(A,1);
  End;
  For I := Low(A) To High(A) Do A[i] := Random(100)+1;
end;