I have about 20 control textbox and i want to change all this backcolor to grey color

i have code :

thisform.textbox1.backcolour = grb(225,225,225)
thisform.textbox2.backcolour = grb(225,225,225)
thisform.textbox3.backcolour = grb(225,225,225)
thisform.textbox4.backcolour = grb(225,225,225)
....... so on


instead of using so many code to make all textbox to grey color,
can i use for loop to shorten the code?

i.e.
for n=1 to 20
txt1=textbox+alltrim(str(n,2))
thisform.txt1.backcolor=grb(225,225,225)
endfor


but is doesnt work!!
anyone can help me on this