I'm trying to disable various fields on a html by using a onchange or onblur event in my selectfield. Rhe problem is, if I try to use it. it will only use one of the select options.

Here is the function I am using:
function purchAddress(Form) {
if (Form.toLoan.value="Purchase")
{
Form.purAddress.disabled="True";
Form.purCity.disabled="True";
Form.purState.disabled="True";
Form.purzCode.disabled="True";
}
else {
Form.purAddress.disabled = "False";
Form.purCity.disabled = "False";
Form.purState.disabled = "False";
Form.purzCode.disabled = "False";
}
}

I realize some of that code is not needed, it's just the result of my tampering trying to get it to work.

And here is the function call.

<SELECT language=javascript id=Select1 onclick="return Select1_onclick()" onblur="purchAddress(shortForm)" name=toLoan>
<OPTION value="Do not Know" selected>Do Not Know</OPTION>
<OPTION value=Purchase>Purchase</OPTION>
<OPTION value=Refinance>Refinance</OPTION>
<OPTION value=""></OPTION></SELECT>

Does anyone know how I can get this to work so that I can freely change values and have the function above still work. I've tried onchange and onblur, but both resutled in the same problem.