Bank statement mapping - Removing trailing values from trx number

We are mapping BAI2 banks statement trx number and we are getting the value of BACS 12345-1 in the banks statement. We want to load this value as 12345 by removing BACS as leading value and -1 as trailing value, can we achieve this in mapping bank statement. We have been able to remove the BACS as the leading value but not able to remove -1 as trailing value.