Shared file problem

I am having the text file name ipaddress.txt which is used to list all the IP address in the network.
There are 3 functions for doing that.
1.runcmd()---> Function is used to track all the IP Addres in the network using the DOS Command(FOR /L %i IN (1,1,254) DO ping -n 1 172.29.116.%i | FIND /i ""Reply"">> c:\ipaddresses.txt).Approximately it will take 15 minutes to complete the list.
2.txtReplace()-->Function is used to repleace the text file content with only ip address.
3.checkIPAddress()-->function is used to check my ipaddress values in the XML file with text file if does not exists alarm will come.
My problem
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In the button click i am running all the 3 functions in the below order 
protected void Button1_Click(object sender, EventArgs e)
    {
        runcmd(); 
        txtReplace(); ...