Hello Everyone

I am very very new to excel, Lots of experience using Microsoft Tsql and Crystal Reports.
I need to force the user to enter their username and password before they are allowed to enter any data.
I have multiple sheets in the workbook, Sheet A has the valid usernames in column a and valid passwords in column b.
In Sheet B for cell L41 I have created a drop down list of usernames from Sheet column a. The user picks their username
and then is forced to enter their password into cell M41. At this point I need to validate the password that was entered into
sheet B cell M41 against the valid combination of (username and password) from Sheet A columns a ans b. I really do not want
to populate any cells with the data from Sheet A, only make sure that the combination of username and password are valid so I
can unlock cell ranges in the sheet. How can I accomplish this task?

Any help will be greatly appreciated
Thanks
JLW SR