ASP.NET Code behind Javascript Problem

Hi all

my java script looks like:

<script language="javas cript">
function showProgress()
{
window.setTimeo ut('sleep()',20 00);
}
function sleep()
{
normal.style.di splay = "none";
inProgress.styl e.display = "block";
}
</script>

my code behind looks like:

btn.Text = resourceManager .GetString("btn Erstellen");
btn.Attributes. Add("onclick"," showProgress(); ");

as you can see i connect my jscript to the clickevent of the button...i only
have one problem...if for example a requiredfieldva lidator shows an error.
The button is then not executed (the code behind part is not executed)...but
the jscript code is executed and that is not what i want...

how can i tell javascript not to execute if an error is on the page?

has anyone a solution for the problem?

thanks for your help!
m.ahrens