You could use a loop to locate the records and then replace the field contents.
This sample Loops thur Records for test::field1 with the contents "abc" and then replace the test::field1 with abcnrsmd
Sample script :
Go to Record/Request/Page [First]
Replace Field Contents [No dialog;test::field1;test::field1 & "nrsmd"]
Go to Record/Request/Page [Next; Exit after last]
Replace Field Contents updates the specified field for every record in your found set, so it's the correct tool to use, but not inside a loop like this. Instead perform a find to pull up just the records you want to update and then do a replace field contents with the expression shown in the previous post.