Need suggestion for webservices synchronous and asynchronous

Hi friends,

I have one small problem. I am using Asp.Net web services in my application. In aspx application i have a condition that

for sample,
if(a=0)
{
//here i call the storedprocedure
//return the value from sp and stored in dataset and bind in datagrid
}
else if(a>0)
{
//here i call the webservices
}

Please look up my above condition. In the else if condition suppose a is greater than zero i wil call webservices. But what i need that suppose the services are not returned the value within 4 seconds, i will need to go to first condition that is call stored procedure. I hope you understand.

How can we achieve this condition. I thought that we can achieve syncronous. But i dont know exactly about it. So please give a suggestion.

Hope yours reply

Thanks
Guvera