Passing amount from user to braintree server - meteor

Question

This Meteor code uses patrickml:braintree, since I do not have access to the braintree submit event in order to send a price to the server for processing.
How can I pass an $$ amount from a html element on the page where the client is clicking to the server?
//client
Template.account.onRendered(function () { //6a
Meteor.call('getClientToken', function (error, clientToken) {
if (!error) {
braintree.setup(clientToken, "dropin", {
container: "payment-form",
onPaymentMethodReceived: function (response) {
var nonce = response.nonce;
Meteor.call('btCreateCustomer', function(error) {
if (error) {
throw new Meteor.Error('customer-creation-failed');
} else {
Meteor.call('createTransaction', nonce, function (error) {
if (error) {
throw new Meteor.Error('transaction-creation-failed');
}
});
}
});
}
});
}
});
});
<template name="account">
<div id="account">
<p>Select invoice period:</p>
<select class={{this.class}} data-id={{_id}} name={{name}}>
{{#each values}}
<option class={{class}} selected={{selected}} name={{name}} value={{value}}>{{{label}}}</option>
{{/each}}
</select>
<br><br>
<form role="form">
<div class="row">
<div class="col-md-6 col-xs-12">
<div id="payment-form"></div>
<button type="submit" class="btn btn-success">Submit</button>
</div>
</div>
</form>
</div>
</template>