I have a spreadsheet with lots of numeric enteries along with some empty cells. 
I want to add a specified number to all the enteries. If the new valse
is greater than or equal to zero I want the cell to be empty.
Otherwise I want the
new number to be specified.

For example

   A       B      C       D
1  name    name1  name2   name3
2  mode1 -0.75    -2.25   4
3  mode2 -0.23    -1.45   
4  mode3          -1.24   -3

and lets say the specified range was a2:d4 and the number was 1.0 
so I would have

   A       B      C      D
1  name    name1  name2  name3
2  mode1   0.25  -1.25    5
3  mode2   0.77  -0.45   
4  mode3         -0.24    -2

then blanking cells greater than 0

   A       B      C      D
1  name    name1  name2  name3
2  mode1         -1.25         
3  mode2         -0.45   
3  mode3         -0.24    -2

I would like to specify the range of cells and also the number to be added.

What is the best way of doing this?

Open your file.
Hit Alt+F11 to open the Visual Basic Editor (VBE) window.
From the menu, choose Insert-Module.
A code window should appear at the right-hand side of your screen.
Paste the following code into that window:

START CODE-----------------

Option Explicit

Sub Macro1()

'Presented By www.vbaexpress.com

Dim Rng1            As Range
Dim Prompt          As String
Dim Title           As String
Dim Value           As Double
Dim c               As Range

    Prompt = "Select the range you want to work with."
    Title = "Range Input"
    Set Rng1 = Application.InputBox(Prompt, Title, Selection.Address, , , , , 8)
    
    Prompt = "Input the number that you want to add to each value."
    Title = "Number Input"
    Value = Val(InputBox(Prompt, Title))

    For Each c In Rng1
        If IsNumeric(c.Value) Then
            c.Value = c.Value + Value
        End If
        If c.Value > 0 And IsNumeric(c.Value) Then
            c.ClearContents
        End If
    Next

End Sub

END CODE ------------------

Hit the SAVE diskette on the toolbar to save the code into the file,
and then close the VBE window.

You can assign this macro to a keyboard shortcut or other object by
going to the help file and looking for this topic:  Assign a macro to
run from a keyboard shortcut, a graphic object, or a toolbar button

I hope this helps!
Sorry if I took any money away from the researchers...

My name is Dreamboat.

Hi Dreamboat,

Thanks! It works perfectly. I know you are not a researcher but is
there anyway to pay you as it is easily worth the $25 to me.

Thank you very very much!!!

Mick