You need to set a Timer event on your form.
Change the Timer interval to 1000 (1 second).
In the On Timer Event, place the following code;
If textboxname.backcolor <> 255 then
textboxname.backcolor = 255
else
textboxname.backcolor = 16777215
end if
Replace textboxname with the name of the text box you want
to blink.
This will make the background flash red then white every
second. Timerintervals are in milliseconds, so 1000
milliseconds = 1 second.
Good Luck!
Steve.