I resolved the probelm. I created two variables :
Def_Val1 = "MyView"
Def_Val2 = "NewId('" + Def_Val1 + "')"
Then issued :
= DBSETPROP("MyView.Primarykey", "Field", "DefaultValue", Def_Val2)

Everything works fine now but I tought that there it was simpler.

Christian Cote