The Quest for the Excel Custom Function Tooltip

The quest for the Excel custom function tooltip

I've posted a proof-of-concept project to GitHub as the Excel-DNA IntelliSense project, implementing this.

Using the UI Automation classes to monitor the appropriate Excel user interface events, a form is displayed when appropriate.

The code is wrapped as an Excel-DNA add-in, and works on my Excel 2013 / Windows 8 machine. I've tested on one other configuration (64-bit Excel 2010 on Windows Server 2008) and had a serious problems.

For a C# function defined with the Excel-DNA attributes like this:

[ExcelFunction(Description = 
    "A useful test function that adds two numbers, and returns the sum.")]
public static double AddThem(
    [ExcelArgument(Name = "Augend", 
                   Description = "is the first number, to which will be added")] 
    double v1,
    [ExcelArgument(Name = "Addend", 
                   Description = "is the second number that will be added")]     
    double v2)
{
    return v1 + v2;
}

we get both the function description

and when selecting the function, we get argument help

That looks nice, but it's all still very flaky, only works on my machine and sometimes crashes Excel. It might be a start, though...

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Update 9 May 2014:

I've made some progress figuring out how to make the argument help work under older Excel and Windows versions. However, it still needs quite a lot of work to get everything reliable. Anyone who would like to help with this should please contact me directly.

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Update 18 June 2016:

Excel UDF IntelliSense support for both Excel-DNA add-ins and VBA functions is now being tested. See the Getting Started page on GitHub for instructions.

How to put a tooltip on a user-defined function

Professional Excel Development by
Stephen Bullen describes how to
register UDFs, which allows a
description to appear in the Function
Arguments dialog:

Function IFERROR(ByRef ToEvaluate As Variant, ByRef Default As Variant) As Variant
    If IsError(ToEvaluate) Then
        IFERROR = Default
    Else
        IFERROR = ToEvaluate
    End If
End Function

Sub RegisterUDF()
    Dim s As String
    s = "Provides a shortcut replacement for the common worksheet construct" & vbLf _
    & "IF(ISERROR(<expression>), <default>, <expression>)"

    Application.MacroOptions macro:="IFERROR", Description:=s, Category:=9
End Sub

Sub UnregisterUDF()
    Application.MacroOptions Macro:="IFERROR", Description:=Empty, Category:=Empty
End Sub

From: http://www.ozgrid.com/forum/showthread.php?t=78123&page=1

To show the Function Arguments dialog, type the function name and press CtrlA. Alternatively, click the "fx" symbol in the formula bar:

Provide contextual help for users on custom functions in Excel formulas

You can press Ctl+Shift+A after typing the function name and it will present the parameter names in the formula bar. If you want an actual tooltip to display, check out this post.

Excel custom function from Power Query

You can't use a Power Query function outside of the query editor, at least not directly in an Excel formula. You can set a table of inputs and run it through a query to get a table of outputs but that requires refreshing the query every time you change the inputs.

How to VBA show tooltip for UDF in runtime?

Unfortunately this isn't possible. Your best option is to use

Application.MacroOptions()

This method enables you to provide descriptions, help etc. when your UDF is added through the Function Wizard.

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