Add this in the INIT of your form:

Local i,color1, R, G, B
With This
.scalemode = 3 &&pixeles
.drawstyle = 0 && sólido
.drawwidth = 2
R=0 'you can change this
G=255 'you can change this
B=0 'you can change this
FOR i = 1 to 255
*-- Disminuimos valor de colores
If r > 0 then
r = r - 1
endif
IF g > 0 then
g = g - 1
endif
IF b > 0 Then
b = b - 1
endif
color1 = RGB(R,G,B)

*Establesco el color
.forecolor=Color1

*- Dibujo linea sobre el fomulario
.line (0,.ViewPortHeight * (i - 1) / 255, .ViewPortwidth, .ViewPortheight * i / 255)
NEXT i
EndWith

I hope this help you.