InvokeURL variables from another form

InvokeURL variables from another form

Hi,
I'm hoping the answer to this is easy and I'm just being dumb... just can't get the syntax right

I have an InvokeURL task that works, but instead of making the same task for each company lookup, I want to substitute values from another Form.

ie. I have a form called 'token' that includes the 'authtoken' and 'Basic auth' encoded parameters for the task.
Here's an example that works- I want to pull the access token and Authorisation parameters from another form (bits in RED)

list GetMosyleStaffList()
{
headerMap = Map();
headerMap.put("Content-Type","application/json");
headerMap.put("accesstoken","77733xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx7f747725a");
        headerMap.put("Authorization","Basic bWV0cxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxQ3YkJsIQ==");
//info headerMap;
parameter_data = Map();
parameter_data.put("operation","list_users");
//info parameter_data;
response = invokeurl
[
type :POST
parameters:parameter_data.toString()
headers:headerMap
];
json_list = response.toJSONList();
users_list = json_list.getJSON("response").getJSON("users");


For bonus points- this external API only responds with 50 records at a time, but some clients have over 50 Staff. How can I iterate this InvokURL call to get the next pages?
The pagination request needs to be in JSON and included in the Body of the request in the form -

{
   "operation": "list",
   "options: {
      "page": "2"
   }
}