Call value from worksheet

Hello,
can anyone tell me how I can work with a value in VBA that is stored in an excel spreasheet?

I want to make an If loop stating that:
[VBA]
If value_in_"User Data!A" & Listbox1.Listindex + 3 = 0 then
Label1.Caption = "User Data!A" & Listbox1.Listindex + 1
End If
[/VBA]

[vba]
If value_in_"User Data!A" & Listbox1.Listindex + 3 = 0 then
[/vba]

:confused4 Maybe I am misreading this, but I do not think so. The value returned by .ListIndex should be -1 to one less that the list count. So as -1 + 3 is already 2......