OK, I have some code for an input box seen here:

Sub AddUnits()
On Error GoTo HandleError
Dim units
Dim newBox
newBox = InputBox("Please enter units", "Units")
HandleError:
End Sub

There are several things I want to do to it but am not quite sure how to achieve them. I have listed them below...

1. I want it so that when the Macro is activated the input starts at Cell 1 in Column C and descends down the column as data is enter. (Example: from Cell 1 to 2 to 3 to 4 and so on as data is entered.)

2. I want it so that when a number of units is entered in the message box for a cell the data in that cell is automatically added to the number entered in the input box. (Example: 25 is in Cell C5 and 10 is entered in the input box, then 35 would show up in Cell C5 and the input box would move to cell C6)

3. I want it so that when a letter is entered in the input box the input box will move to a different column and start at the first cell in that column and do the same thing as the others. (Example: The input box is in Cell C20 and A is entered, the input box would then shift to cell J1 and data entry would begin there.

4. I also have some code that will close the program and save, is there anyway to make code to put a button on the input box for that?

If you even know part of this that would greatly help. Any suggestions or assistance is greatly appreciated.