Retain the last value read from a csv file in the textbox control of the application.

I am running a data-driven test for the log-in functionality of my application. The input is coming from a csv file. The file structure is very simple : Two columns - 1. User Id and 2. Password. The data is a combination of words with comma ","  as seperator. The last row of the "table" is the correct log-in and password - which has to grant access to the application - ie open/load  the application. After each combination of user-id and password is populated a message saying "invalid input " is displayed . Control goes back to the  "userid" text box and the next userid is entered and so on so forth untill the last "row" is entered. Problem is as soon as the last value ie "password" is entered in the textbox control, and in the split second it takes to click the "ok" button, the entered value from the textbox is emptied ie field is cleared and application does not load. But the test still passes , but I want the value to be retained and application loaded as soon as the last "row" is read into the controls. Is there a way to retain the last value read into the textbox control and if so please do let me know how this problem can be solved.  Thank You.