Creating a User‑Defined Function
in Excel using VBA
Microsoft Office Training
Excel Training
www.bluepecan.co.uk

• Excel includes many different functions that
help you complete calculations, but have you
ever wished for a function that that doesn’t
exist in Excel? If you have, this tutorial will
explain how to create a function DIY style.
www.bluepecan.co.uk

• You create custom functions in the Visual
Basic Editor (VBE) which you can get to by
clicking Tools > Macro > Visual Basic Editor or
by using the shortcut key ALT F11. If you are
using Excel 2007 click on the Developer ribbon
and then click on the Visual Basic button.
• Once in the VBE environment you will need to
create a module to hold your function. Click
Insert > Module
www.bluepecan.co.uk

• A function is defined with a name (for the
function) and if necessary between 1 and 60
arguments. For example the Excel worksheet
function VLookup has 4 arguments.
www.bluepecan.co.uk

A func tio n with no arg ume nts
• Several VBA functions such as rand() have no
arguments. In the same way you can create
custom functions that have no arguments.
The following function will display the path
and filename of the active workbook.
www.bluepecan.co.uk

Function File()
File = ActiveWorkbook.FullName
End Function
• Notice the function starts and ends with
‘Function’ rather than sub.
www.bluepecan.co.uk

• Enter =File() into a worksheet to see the
result.
or
• Click on fx (Insert Function) and open the User
Defined category to see your function listed
here
www.bluepecan.co.uk

• The next function displays the username (as
set in Tools | Options | General)
Function User()
User = Application.username
End Function
www.bluepecan.co.uk

A Cus to m Func tio ns with Arg ume nts
• The following function simply calculates a value plus
VAT. In an empty worksheet create a column of
prices.
• Then switch to the VBE environment and in a module
create the following custom function. Notice that
with this function you need to place arguments in
the brackets after the function name.
• The sales argument will require you to select the cell
containing the sales value for which you wish to add
the VAT to.
www.bluepecan.co.uk

Function vat(sales)
vat = sales * 1.15
End Function
• Use the VAT function to calculate the VAT
inclusive value in your list of prices
www.bluepecan.co.uk

• We could also add a markup value as part of
our function by adding a second argument.
www.bluepecan.co.uk

Function retail(sales, markup)
retail = sales * (markup + 1) * 1.15
End Function
www.bluepecan.co.uk

• Enter a markup percentage on your worksheet
and refer to this value in the second argument
of the function (separated from the first by a
comma).
• You can always use the functions argument
dialogue box to enter cell references or
values.
www.bluepecan.co.uk

• The following function calculates the amount
of time that has elapsed between a start time
and the end time.
• The function also works for times over two
separate days, in other words when the start
time is greater than the end time.
www.bluepecan.co.uk

Function CalTime(StartTime, EndTime)
If StartTime > EndTime Then
CalTime = EndTime - StartTime + 1
Else
CalTime = EndTime - StartTime
End If
End Function
www.bluepecan.co.uk

• See this Excel training tutorial on the Blue
Pecan website
www.bluepecan.co.uk