Javascript question

I have a validation in my .asp page and wanted to alter it so the client
cannot place a space in the [ServiceFormat_OtherDesc] field, because now the
client cannot leave the field blank, but they can place a space in the field
and it will be accepted. Any help would be greatly appreciated. Thanks

function Validate(){
i=0
chosen = ""
for(i=0; i<document.Page3["ServiceFormat"].length; i++){
if(document.Page3["ServiceFormat"][i].selected){
chosen = chosen + document.Page3["ServiceFormat"][i].value
if(document.Page3["ServiceFormat"][i].value == "06" &&
document.Page3.ServiceFormat_OtherDesc.value == ""){
alert("Please Fill In Service Format Other Description");
document.Page3["ServiceFormat"].focus();
return false;}
}
}