Creating a Plus/Minus Button

@Micky: your solution does erase the formula.

@Don: "On Error GoTo 0" is not needed in this case because there is no code following the statement that can cause the error. After ending the "For Each" follows the "End Sub" and that resets the On Error anyway.

I had the same problem with it erasing the formula. I agree with Willy that the Cell.HasFormula is the key and WRosocha's suggestion to use "-cell.Value".

However, I do have an issue using "On Error Resume Next" to replace condition validation. Further heartburn when it comes to Functions and Subs that have an opening "On Error Resume Next" and no "On Error GoTo 0". When "On Error Resume Next" is used it just be just prior to the code line(s) where errors are acceptable. Immediately after should be the "On Error GoTo 0".

I also prefer using the VBA native functions instead of Application or Worksheet function. I've added a Len(Trim(cell.Value)) > 0 for the difference between the two.

That rant aside, here's my suggestion:
Sub PlusMinus()
Dim cell As Range
For Each cell In Selection
If Len(Trim(cell.Value)) > 0 _
And IsNumeric(cell) _
And Not cell.HasFormula _
And Not IsDate(cell) Then
cell.Value = -cell.Value
End If
Next cell
End Sub

@Willy,
This is a little shorter and seems 2 B working fine:
Sub PlusMinus()
On Error Resume Next
For Each CL In Selection
CL.Value = -CL
Next
End Sub
Michael (Micky) Avidan
“Microsoft® Answers" - Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2014)
ISRAEL

Willy,

Thank you for the additional insights.

This tip claims that formulas are left intact. That is not the case. When a cell contains a formula this macro replaces it with it's negative result. So the formula is gone. To prevent this we have to test whether the cell contains a formula.

'cell.Value = -cell.Value' generates an error when cell.Value isn't a number. So let's use this in this simplified macro that does what it is expect to do:

Sub PlusMinus()
Dim cell As Range
On Error Resume Next 'copes with cells that are not numeric
For Each cell In Selection
If Not cell.HasFormula Then cell.Value = -cell.Value
Next cell
End Sub

Cells containing a formula, a label or a date are left untouched.

Why would you invoke the MULTIPLY operation to flip the sign bit?

This violates the principle of using the simplest programming constructs. It also invokes heavy duty computation in the CPU.

Why not use

cell.Value = -cell.Value

Are there cases where this wouldn't work?