function checkField(oElem){
	if(oElem.value == ""){
		alert("Please fill in the required field");
		oElem.focus();
		return false;
	}else if((oElem.value.indexOf("'") != -1) || (oElem.value.indexOf(":") != -1) || (oElem.value.indexOf("~") != -1)){
		alert("You have entered an invalid character");
		oElem.focus();
		return false;
	}else{
		return true;
	}
}