Payment - Shipping relationship. Is it possible?

Hey
I have created two new simple modules:

• "Pickup in the store" shipping module
• "Payment on picking up in the store" payment module

As you can imagine they are literally not doing anything, just setting proper order status. 
I would like to disable "Payment on picking up in the store" payment module when "Pickup in the store" is not selected as a shipping method. Is there an easy way to do so?

These modules should already do what you ask.
https://www.litecart.net/en/addons/49/pickup

Thanks, @tim :) I didn't notice this addon earlier.
But it is not working.  

From what I see from var_dump, $shipping variable has ['data']['selected'] field empty regardless of what shipping method I pick during the checkout. 

object(mod_shipping)#12 (3) { ["data"]=> array(2) { ["selected"]=> array(0) { } ["userdata"]=> array(0) { } } ["items"]=> array(0) { } ["modules"]=> array(4) { ["sm_poczta_polska"]=> object(sm_poczta_polska)#27 (9) { ["id"]=> string(16) "sm_poczta_polska" ["name"]=> string(13) "Poczta Polska" ["description"]=> string(0) "" ["author"]=> string(8) "skoruppa" ["version"]=> string(3) "1.0" ["website"]=> string(0) "" ["settings"]=> array(6) { ["status"]=> string(1) "1" ["icon"]=> string(34) "/images/shipping/poczta_polska.jpg" ["delivery_time"]=> string(7) "2-5 dni" ["handling_fee"]=> string(4) "8.00" ["tax_class_id"]=> string(0) "" ["priority"]=> string(1) "0" } ["status"]=> int(1) ["priority"]=> int(0) } ["sm_pickup"]=> object(sm_pickup)#31 (9) { ["id"]=> string(9) "sm_pickup" ["name"]=> string(6) "Pickup" ["description"]=> string(0) "" ["author"]=> string(17) "LiteCart Dev Team" ["version"]=> string(3) "1.0" ["website"]=> string(23) "http://www.litecart.net" ["settings"]=> array(4) { ["status"]=> string(1) "1" ["icon"]=> string(0) "" ["geo_zone_id"]=> string(0) "" ["priority"]=> string(1) "0" } ["status"]=> int(1) ["priority"]=> int(0) } ["sm_zone_weight"]=> object(sm_zone_weight)#14 (9) { ["id"]=> string(14) "sm_zone_weight" ["name"]=> string(40) "Koszty wysyłki dla stref geograficznych" ["description"]=> string(0) "" ["author"]=> string(17) "LiteCart Dev Team" ["version"]=> string(3) "1.0" ["website"]=> string(23) "http://www.litecart.net" ["settings"]=> array(14) { ["status"]=> string(1) "0" ["icon"]=> string(0) "" ["weight_class"]=> string(2) "kg" ["geo_zone_id_1"]=> string(0) "" ["weight_rate_table_1"]=> string(0) "" ["geo_zone_id_2"]=> string(0) "" ["weight_rate_table_2"]=> string(0) "" ["geo_zone_id_3"]=> string(0) "" ["weight_rate_table_3"]=> string(0) "" ["weight_rate_table_x"]=> string(15) "5:8.95;10:15.95" ["method"]=> string(4) "<" ["handling_fee"]=> string(4) "0.00" ["tax_class_id"]=> string(0) "" ["priority"]=> string(1) "0" } ["status"]=> int(0) ["priority"]=> int(0) } ["sm_country_based_shipping"]=> object(sm_country_based_shipping)#13 (9) { ["id"]=> string(25) "sm_country_based_shipping" ["name"]=> string(22) "Country Based Shipping" ["description"]=> string(0) "" ["author"]=> string(17) "LiteCart Dev Team" ["version"]=> string(3) "1.0" ["website"]=> string(23) "http://www.litecart.net" ["settings"]=> array(7) { ["status"]=> string(1) "0" ["icon"]=> string(0) "" ["weight_class"]=> string(2) "kg" ["rate_tables_map"]=> string(7) "PL;;pol" ["rate_tables"]=> string(6) "pol;:8" ["tax_class_id"]=> string(0) "" ["priority"]=> string(1) "0" } ["status"]=> int(0) ["priority"]=> int(0) } } }

Hmm.. that does not sound right. Maybe I should look into it. It should carry your last choice of shipping. $GLOBALS['shipping']->data['selected'] should return the choice of shipping for your current session. Is it the same if you access session::$data['shipping']['data']['selected'] ?

Thanks again!

session::$data['shipping']->data['selected']['id']
is working just fine :)