// JavaScript Document
function precheckPostNr(curobj)
{
	curval=curobj.value;
	
	if(curval.length==1)
	{
		var code=curval.charCodeAt(0);
		if(code<48 || code>57)
		{
			curobj.value="";
			return false;
		}
	}
	if(curval.length>1)
	{
		for(var i=2; i<=4; i++)
		{
			var code=curval.substr(i, 1).charCodeAt(0);
			if(code<48 || code>57)
			{
				curobj.value="";
				return false;
			}
		}
	}
	
	if(curval.length==4)
	{
		var code=curval.substr(1, 3).charCodeAt(0);
		if(code<48 || code>57)
		{
			curobj.value="";
			return false;
		}
		document.getElementById('imageChkPostNr').disabled=false;
		return true;		
	}
	if(curval.length>4)
	{
		return false;
		curobj.value=curval;
	}
}