Change Cell Contents With Conditional Statement

i am trying to automate altering a DAT file. Basically, each line of data in the DAT file contains an entity name, an account name, and a value. for some of the accounts, i need to change the entity name. for all other accounts, i can leave the entity name alone. if i copy the DAT file into Excel, and use text to columns, how can i create a macro to compare the accounts to a range of cells containing a list of the accounts i need to alter the entity name for, and then change the entity name if there is a match?

the account does not need to match perfectly, the accounts i input only needs to contain the reference account. the list of accounts and the entity name i need to change to are in cells on another sheet. i thought about doing a loop to run through each line of data, but i am not sure how to do that.