Replace text at specific position in string using VBA - excel

Question

I want to replace a substring (substring_a) with another substring (substring_b) within a string by specifying the position and length of substring_a.
I'm trying to use the Mid function, but it doesn't seem to work unless substring_b is equal to or longer than substring_a
Here is my code:
Sub Test_Mid()
Dim starting_text As String
Dim replacement_text As String
starting_text = "Long Starting Text"
replacement_text = "End"
Mid(starting_text, 6, 8) = replacement_text
MsgBox (starting_text)
End Sub
I want the code to return "Long End Text", but instead it returns "Long Endrting Text".
How do I fix this?
Note: The above is an illustrative example. I can't use the Replace function directly with the replacement_text because in my actual macro, replacement_text is variable.

Answer 1

You are making a simple thing overly complex. All that is needed is a simple replace.
starting_text = Replace(starting_text, "Starting", "End")
To replace just the 1st occurrence, use this:
starting_text = Replace(starting_text, "Starting", "End", 1, 1)
Or if it's just one occurrence, starting at a specific location, use this:
starting_text = Replace(starting_text, "Starting", "End", Instr(starting_text, "Starting"), 1)
Or if it's just one occurrence, starting at a specific location, and you dont want it to be case sensitive, use this:
starting_text = Replace(starting_text, "Starting", "End", Instr(starting_text, "Starting", vbTextCompare), 1, vbTextCompare)
VBA Replace Function

Answer 2

Below is my solution:
Sub Test_Mid()
Dim starting_text As String
Dim replacement_text As String
Dim replaced_text As String
starting_text = "Long Starting Text"
replacement_text = "End"
replaced_text = Mid(starting_text, 6, 8)
starting_text = Replace(starting_text, replaced_text, replacement_text)
MsgBox (starting_text)
End Sub
Note: For the example code here, #brax's solution is more efficient, but this code above shows how to replace text at a specific position (which is what I need for my actual use case).

Answer 3

Replacing a string in string in VBA is an easy taks, if Replace() is used.
Anyway, if Replace() is to be omitted, then it becomes more interesting. Theoretically, the string could be splitted always into 3 parts:
First Part - String To Replace - Last Part
Even when the FirstPart or/and the LastPart are with length 0, the division is to be made. Then, removing StringToReplace from the string completely and in its position, write the new string. The position is determinted with IsStr. It could be used as a function, using error handlers to return the initial expression, if the find is not part of the string:
Function Replace2(expression As String, find As String, replace As String) As String
On Error GoTo replace2_Error
Replace2 = expression
Dim position As Long: position = InStr(1, expression, find)
Replace2 = Left(expression, position - 1)
Replace2 = Replace2 & Mid(expression, position + Len(find))
Replace2 = Left(Replace2, position - 1) & _
replace & _
Right(Replace2, Len(Replace2) - position + 1)
Exit Function
replace2_Error:
Replace2 = expression
End Function
And the tests of the function:
Sub TestMe()
Debug.Print Replace2("1", "", "")
Debug.Print Replace2("1", "", "2")
Debug.Print Replace2("", "3", "")
Debug.Print Replace2("32", "a", "")
Debug.Print Replace2("My Very Interesting Long Starting Text", "Starting", "Ending")
Debug.Print Replace2("My Very Interesting Long Text Starting", "Starting", "Ending")
Debug.Print Replace2("Starting My Very Interesting Long Text", "Starting", "Ending")
End Sub