MSCOMM32.OCX (Drop an ActiveX control on a form, choose Insert control, and pick Microsoft Communication Control, version 6.0).
You may need to adjust the 'port' property, the 'settings' property (baud rate, parity, data bit, and stop bit values), the InBufferSize, etc.
Open the port:

thisform.olecontrol1.portopen=1

Use the 'Input' method to read data:

thisform.textbox1 = thisform.olecontrol1.input