example
A1 row entered data time should be show in B1
A2 row entered data time should be show in B2

You need to add a VBE (Visual BASIC for Excel) function to each A1 row cell that does the following when the enter key is pressed, it calls the Now() function and adds to add the current date and time to the corresponding B row cell. I am NOT familiar with Excel so much, but I AM with spreadsheets in general operated under Visual BASIC, which can add functions using visual basic embedded in a cell triggered by the ENTER key event. In essence, this would keep track of the most recent entry OR edit of the cell. So, the date and time would be either the initial entry OR the most recent EDIT of the cell data.

The other person who said CTRL SHIFT : (Control plus shift plus COLON sequence) inserts the TIME in the current cell, MANUALLY. CTRL : (Control plus colon) inserts the current DATE in the current cell, MANUALLY. I am thinking you want date and time inserted when the user hits the enter key to fix the data entry so the user does NOT have to manually add the date and then the time. You need the VBE function, NOT manual entry.