Online Customer Form using 'nlapiSetFieldValues' during PageInit

I was wondering if there is a way to use the 'nlapiSetFieldValues' suitescript function within the Online Customer Form's Page Init Function.

I have an inquiry form that allows the end user to select which category they are, but we dont want ALL the categories to display on the select field. Currently, when the customer form displays, all of the categories are displayed...

Any way to filter the results, or explicitly state which values are to be displayed on the dropdown? The below code snippet is what I have now, which does not work.

function Online_Inquiry_PageInit(type){    var values = new Array(); // define a new Array  values[0] = '1';  //internal ID of first category, parent  values[1] = '2';  //internal ID of the second category, student  nlapiSetFieldValues('category',  values, false, true);  }