Question : Excel 2000: Validate an existing time or date

Hi all,

I have an existing string, that is supposed to be a valid time or date, already entered into a cell that is formatted as Date.

I want to know how I can verify that the cell content is in fact a valid date or time.

Yes, I have seen the answer to a previous question on how to check if a string is in an appropriate format for converting into a date/time, but this is slightly different. Is there not some sort of cell property like .IsValid that you can read to see if the value containd therein is valid for the cell's defined format?

(I am a newbie Excel programmer - but an old timer programmer in other things. Seems to me that this is a simple question for anybody with a bit of experience.)

tia

avi

Answer : Excel 2000: Validate an existing time or date

The reason why Malic's function doesn't work is because DateValue returns an error if it is handed a non-string input, and a valid date is a long. This is why I use the Case statement, to test longs and strings separateley.

I didn't test for a Date variable, since I didn't think you could retrive a Date from a cell (still can't stop thinking about a function that you would be calling from the spreadsheet instead of VBA :) ). None-the-less, there is no reason why my function should return False if you feed it a VB date type, so I have revised for that case.


Option Explicit

'Returns True if DateValue is a valid numerical or string date.
Private Function IsValidDate(DateInput As Variant) As Boolean
   Dim varDateValue As Variant

   Select Case VarType(DateInput)
      Case vbDecimal, vbDouble, vbInteger, vbLong, vbSingle
         IsValidDate = DateInput >= 0 And DateInput <= 2958465
     
      Case vbString
         On Error Resume Next
         varDateValue = DateValue(DateInput)
         'On Error GoTo 0
         IsValidDate = Not (IsEmpty(varDateValue))
         
      Case vbDate
         IsValidDate = True
     
      Case Else
         IsValidDate = False
   End Select

End Function


Private Sub Test()

   MsgBox IsValidDate(#12/7/2005#)
   
   MsgBox IsValidDate("January 1, 2006")
   
   MsgBox IsValidDate("January 41, 2006")

   MsgBox IsValidDate(5000)
   
End Sub