I am trying to write a function to find the first line of an external worksheet. I can do this with a sub, but it is not working as a function. can it be done.
Currently I am using
Function GetLine(fileName As String) As Boolean GetLine = 0 Dim loadBook As Workbook If loadBook = Application.Workbooks.Open(fileName) Then GetLine = True Else GetLine = False End If end function
I am getting a return of #value. I think this is because of an error in loading the workbook.
Please advice and thank you.
That’s right, execution of user-defined functions has certain limitations. There is few tricks to do what you want within UDF and not to violate an order.
1. Get another instance of Excel.Application via late binding, open workbook with it, perform all the necessary calculations by referring to the instance. It’s critical to refer exactly to the created instance, so that some nested
With ... End With statements or additional syntax e. g. before
.Sheets() may seem unusual. There is an UDF example how to obtain the first line on the sheet from the closed file:
Function GetFirstRowLbind(FileName, SheetName) ' UDF function that calculates value, works with certain limitations On Error Resume Next With CreateObject("Excel.Application") ' late binding .Workbooks.Open (FileName) GetFirstRowLbind = .Sheets(SheetName).UsedRange.Row .Quit End With End Function
OERN used only to skip errors like missing file and others so that
.Quit statement be surely executed to prevent memory leakage, otherwise launched excel processes will stay in memory after each sheet recalc and UDF call.
2. Implement some UDF extending by scheduling to another procedure the actions that should be done after the UDF completion, with execution based on the sheet recalc event. This way more complex and hard to debug, but more flexible and it gives opportunity to do much more “within” UDF, like changing neighbour cells, or even any accessible data in the whole application. Example with scheduling:
Place code to one of the module of VBAProject:
Public Tasks, Permit, Transfer Function GetFirstRowSched(FileName, SheetName) ' UDF function, schedules filling this UDF cell with a value after all UDFs to be completed If IsEmpty(Tasks) Then TasksInit If Permit Then Tasks.Add Application.Caller, Array(FileName, SheetName) ' pack arguments to array, the dictionary key is actually this cell object GetFirstRowSched = Transfer End Function Sub TasksInit() ' function for initial setting values Set Tasks = CreateObject("Scripting.Dictionary") Transfer = "" Permit = True End Sub Function GetFirstRowConv(FileName, SheetName) ' function that actually calculates the value, runs without UDF limitations like an usual function With Application.Workbooks.Open(FileName) GetFirstRowConv = .Sheets(SheetName).UsedRange.Row .Close End With End Function
Place code to ThisWorkbook section of Microsoft Excel Objects in VBAProject:
Private Sub Workbook_SheetCalculate(ByVal Sh As Object) ' sheets recalc event that perform all scheduled calls, puts data to each of UDFs cells Dim Task, TempFormula If IsEmpty(Tasks) Then TasksInit Application.EnableEvents = False Permit = False For Each Task In Tasks ' cycle trough all stored cell objects TempFormula = Task.FormulaR1C1 Transfer = GetFirstRowConv(Tasks(Task)(0), Tasks(Task)(1)) ' unpack arguments from array to perform calculations Task.FormulaR1C1 = TempFormula Tasks.Remove Task Next Application.EnableEvents = True Transfer = "" Permit = True End Sub
If the UDF is being called from a cell, it can only return a value to that cell. It cannot open another workbook