VBA: keypress

Not sure what you are looking for. You can always get the value of the active cell by Activecell.value whether you arrived there with a tab or other means shouldn't matter. Do you mean you want the value only if the cell was entered with a tab key and you want something to tell you when the tab key was pressed?

The keypress command does not work on TAB. You could try this but its probably not quite what you are looking for.
Place this code in the sheet1 module:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Application.OnKey "{TAB}", "SeeVal"
End Sub

..and this code in module1:

Sub SeeVal()
Cells(ActiveCell.Row, ActiveCell.Column + 1).Select
MsgBox ActiveCell.Value
End Sub

This wiil make the cursor TAB right and display a msgbox with the cell value.
The downside is that using OnKey disables & over-rides the regular TAB behaviour.