Excel to email with replace text in Premade Email Template - excel

Question

I'm using the below code to auto-generate an email.
Public Function GenerateEmail(sendToText As String, _
sendCCText As String, sendBCCText As String, _
subjectText As String, fileName As String)
Application.ScreenUpdating = False
Dim OutApp As Object
Dim OutMail As Object
Set OutApp = CreateObject("Outlook.Application")
Set OutMail = OutApp.CreateItemFromTemplate(fileName)
With OutMail
.sendTo = sendToText
.CC = sendCCText
.BCC = sendBCCText
.Subject = subjectText
.HTMLbody = WorksheetFunction.Substitute(OutMail.HTMLbody, "%TESTNUM%", "98541")
.Attachments.Add (Application.ActiveWorkbook.FullName)
.Display
End With
On Error GoTo 0
Set OutMail = Nothing
Set OutApp = Nothing
With Application
.ScreenUpdating = True
.EnableEvents = True
End With
End Function
My end goal is to add data into the email and attach the active document into it as well. Everything here is working as intended, except the .HTLMbody section. It's giving me an error
"Unable to get the Substitute property of the WorksheetFunction
class."
Am I missing a reference to a library? Should I be using something different?
The email is saved as .oft format, so I have a line in the email that has %TESTNUM% that I'm looking to replace with 98541 (or any other string I need to pass into the function)

Answer 1

I have HTML email working in Excel using very similar code. The difference is that I build a temporary string with the text and you could do your substitute code on the string.
Then you can simply use:
.HTMLbody = temp_string
It might not be as elegant but it will help you work out where the problem is.