Detect when a specific color appears on specified on screen area

Hi gurus, im very new to vb and could really use some help with this.

Im trying to write a simple exe to detect a chosen color pixel within a specified area on the screen and sound an alert if that specified color shows up.

so first i need to select an area to monitor, and choose a color to detect and sound an alert when that color shows up.

please help. thanks in advance.