Pass argument in view from custom form
Assuming the custom form sits in its own page. You can rewrite the output of the field, using replacement patterns, in the view to pass the required information as part of the url. 

Then using hook_menu, define parameters to pass to the form 

function hello_world_menu() {
  $items=array();
  $items['hello_world/%/%'] = array (
    'title' =&gt; 'My Custom Form',
    'page callback' =&gt; 'hello_world_form_function',
    'page arguments' =&gt; array(1,2),
    'access callback' =&gt; TRUE,
    'type' =&gt; MENU_CALLBACK,
);
return $items;
}