Validating form field existence then value

[bamboo]

I'm trying to figure out how to first validate that a form field exists, if so, then to validate whether it is empty. If the field doesn't exist then move onto to the next field. I have an 8 field form and I only need to do this double validation on 2 of the fields. This is a CF application where depending on what type of request it is, the particular field will display (either Cash or Stock text field). So here are the two fields that I need to validate. This of course is the bare bones script I'm starting out with assumming both field are present.

function Validate()
{

//validate stock field
if (document.capsia_form.stock.value="")
{
alert("Please enter a stock amount");
return false;
}

//validate cash field
if (document.capsia_form.cash.value="")
{
alert("Please enter a cash amount");
return false;
}

return true;
}

 

[maff500]

to see if a form input box exists, use the if statement like so-
if(document.capsia_form.cash) {
alert("cash amount input box does exist")
}