color SO Header Customer# defined by AR_Customer Type

Trying to color the SO header customer# field if the customer type fall = specific value. I appreciate if you can help.

Ctype = ""

retVal = oBusObj.GetValue("CustomerType$", Ctype)

If Ctype = "SDIS" then
Set myUIObj = oSession.AsObject(oScript.UIObj)

myUIObj.SetControlProperty "CustomerNo$","BackColour$","RED"

End If