validation expression through code behind

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ASP.NET

using multiline text box & pass case id like 1660,1713 in this format also special character i.e (,) between two case id configure through web.config file .
for that i am code in

string s1, s2
 s1 = @"^\d*[0-9](|";
       s2 = @"|\s)\d*[0-9]*$";

     string regx = s1 + Functions.ToString(ConfigurationManager.AppSettings["BulkCaseSeparator"].ToString() + s2);

       RegularExpressionValidator1.ValidationExpression = regx;  

it is working fine when i am pass value in multiline text box like 1660,1713 but not working for 1617,1700,1415 also not working for 1617,1700,1415(this three on first line),1713(it is on second line). what can do for this scenario using above code.