Saving to App.Config

thank you guys for your reply,
p_davis, when i am trying to assign value to kvcs.Vaue i get the following error:
"Object reference not set to an instance of an object." and i create the line above it, which allows me to retrieve value from my config file just fine, so it must have been initialized, i don't know why i am getting this error.
the following line worked for me:
txtSomeTextBoxValue.Text = config.AppSettings.Settings["someKeyVariable"].Value.ToString();

PS:
in your code:
kvce.value = txtSomeTextBoxValue.Text;
how does the kvce value know to which appSetting variable will it save to? I mean my appSetting will have something like:
AppSettings.Settings["someKeyVariable1"].
AppSettings.Settings["someKeyVariable2"].
AppSettings.Settings["someKeyVariable3"].

and you say: kvce.value = txtSomeTextBoxValue.Text;
will you be assign the kvce value to someKeyVariable1 or someKeyVariable2 or ..etc

thank you for your help

I am raising the points to 250

thanks davis, we are almost there,
two questions:
1- I guess when in run mode the app file becomes app.exe.config and when in solution its app.config? is that why the results show only in app.exe.config?
2- if i have more than one AppSettings variable should i create the following:
kvce1 = config.AppSettings.Settings["someKeyVariable1"];
kvce2 = config.AppSettings.Settings["someKeyVariable2"];
... etc ?

thanks again