I found a interesting bug in VFP, which can be solved by the apparently redundant sentence THIS.VALUE=THIS.VALUE. To show the bug:

CREATE a table with a numeric field and a text field.

APPEND a record to it

Create a blank form, and include the table in its environment.

Add a spinner to the form; set its ControlSource to the numeric field, and in its INTERACTIVECHANGE code write THISFORM.REFRESH().

Add a textbox to the form; set its ControlSource to the text field, and in its REFRESH code write THIS.VALUE = STR(THISFORM.SPINNER.VALUE).

Run it, and try to change the spinner by clicking on its arrow buttons!! What I get is: the spinner changes for an instant, and goes back to its original value. (This doesn´t happen if the objects have no ControlSource.)

The solution? Add THIS.VALUE=THIS.VALUE at the beginning of the SPINNER.INTERACTIVECHANGE code.

Weird!!