Put ALL of this in your ThisWorkbook module. Change sheet2 to your sheet
name. Fire the setwhichmonth to test or reset.

'============
Public whichmonth

Sub setwhichmoth()
whichmonth = 1
End Sub
'=========
Sub workbook_open()
On Error GoTo endit
If Month(Date) whichmonth Then nm = Month(Date)
If DateSerial(Year(Date), nm, 1) = _
Application.Run("ATPVBAEN.xla!Workday", nm - Day(nm), 1) Then
With Sheets("sheet2").Range("k12")
.Value = .Value + 100
End With
whichmonth = Month(Date)
End If
endit:
End Sub
'=======
--
Don Guillett
SalesAid Software

wrote in message
ups.com...
A12 = Microsoft


O12 = the market value of my microsoft shares.
M12 = the number of Microsoft shares I currently own
N12 = the current price of each share.
G12 = the amount of money I invest into Microsoft each month ...
always the same monthly investment
H12 = the day of the month (call it the 1st) that I make the monthly
investment .... always the same day .... unless it is not a business
day

I need a formula or macro that would re-calculate cell M12 after I
make each monthly investment.


Summary.... on May 31st, I owned 4000 Microsoft shares. On the 1st I
bought 100 more. I need M12 to update to 4100 when I run the macro.
Can the macro be programmed to run only once each month?