how to reference a variable field name

[IndyB]

In my javascript function I need to use the opener js command to reference a field on a previous page. The problem is that the field name is a variable. If I hard code a variable name into the opener statement, it works fine, but if I try to use the variable I've created, it doesn't work.

Here I define the variable field name:
ineligible_field_name = '#url.ineligible_field#';

Here I try to reference that field name in the opener:
opener.document.frmpage.ineligible_field_name.value = ineligible;

But this doesn't work. Any ideas?

[gil davis]

opener.document.frmpage[ineligible_field_name].value = ineligible;

[IndyB]

Thanks gil !