strErrorMessage = "Please use correct number.";
In case you want to insert any skip patter on QG questoins. you need to use some constructed list. First create predefined list with 2 variables, let's saya 1 as valid and 2 invalid. In constructed list, check all digit cobination if these are valid add 1 from predefined list otherwise 2. On QG questions use pre skip if Listvalue(Constructedlist,1)==1 to to next question.
Let me know for more help.