How to define search string to update the encashment date in check register

HI experts,

I have an issue with the check . the check encashment date is not getting updated . we are using electronic bank statement and the bank statement files are MT940 format . the EBS is working fine but in case of check payment we receive a 12 digit check number i.e ( 000000001618) in the MT940 files where as in the SAP system we have maintained check lot with a 10 digit number i.e ( 0000001618) i have already defined the interpretation algorithm and the search string but the search string only works when i change the sap system check lot to 12 digits as per the MT940 files. How can i define a search string to clear the 12 digits check number in MT940 with the 10 digit in system so that it get cleared and the check encashment date get updated in check information .

could anyone help me .

Thanks