Try setting minigame variables with strings.
Say you want to store for BL_ID 37479 (randomly typed), you set the minigame variable "<var:cl_BL_ID>bidstore" as "<var:cl:BL_ID>", so that you have "37479bidstore" (37479 bank ID storage) equal to their BL_ID. Make sure you check this through VCEifValue before every check or transaction. Also make sure you make a second variable, "<var:cl:BL_ID>bmastore", which returns "37479bmastore" (37479 bank money amount). This is where you conduct transactions. The amount of money that you have in the bank is assigned to that.