How to reset counting?

Hi,

I'm sorry because i don't know where i can post this thread,

I have a form as below

When I input value into textbox No1, this textbox automatic change to read only = true

After I input into tetxbox No2, Q'ty will be change 1/2 until it's become 2/2.

In this time textbox No1 change from read only = true to false and q'ty will be reset to 0 and counting again,

My code is example but it's working not true:

int count = 0;  
  
if ( clause )  
  
{  
  
count++;  
  
txtqty.Text= count.ToString();  
  
}  
  
if ( count ==2)  
  
{  
  
txtNo1.ReadOnly = false;  
txtNo1.Clear();  
txtNo1.Focus();  
txtqty.Text = "0";  

So please help me to solve this troule.

Thank you!