I am using VBA code to make a simple calculator in Excel, please help me to modify the code so that it can complete the following tasks, thank you very much :

Extending the Calculator to Work with Multiple$-$Digit Numbers

Increasing the Size of the Calculator Memory

Calculating the Result Using Recursion

Here is the uncomplete code:

$\text{'}$ The memory of the calculator as an array

$\text{'}$ You need to change the size of the memory to something bigger

Dim Memory$(1$ To $3)$ As String

Dim CurrentPos As Integer

Function CalcTotal$($ByVal Pos As Integer$)$ As Long

$\text{'}$

$\text{'}$ Task $4$: Calculating the Result Using Recursion

$\text{'}$

$\text{'}$ Case $1$: if Pos is bigger than what you have in the Memory array

$\text{'}$ Nothing is available

$\text{'}$ Case $2$: if Pos is exactly at the end of the Memory array

$\text{'}$ Return the number in the position

$\text{'}$ Case $3$: Memory$($Pos$)$ is a number and Memory$($Pos $+1)$ is an operator

$\text{'}$ Return the number in the current position together with the rest of the Memory array

$\text{'}$ Please delete this line after you finish the function

CalcTotal $=0$

End Function

$\text{'}$ This subroutine clears the calculator memory and put an initial value in the calculator

Sub ClearMemory$($ByVal InitialValue As String$)$

$\text{'}$ Put the initial value in the Memory array's first entry

Memory$(1)=$ InitialValue

$\text{'}$ Reset the position to the first position

CurrentPos $=1$

End Sub

$\text{'}$ This subroutine handles the user input by reading the input value InputButton.

Sub HandleUserInput$($ByVal InputButton As String$)$

Dim Display As String

$\text{'}$ Remember the current display of the calculator

Display $=$ Range$("$Display$").$Value

$\text{'}$ This If statement prevents the calculator from crashing when the CurrentPos is $0,$

$\text{'}$ which happens when you suddenly stop the VBA code from running

If CurrentPos $=0$ Then

ClearMemory $"0"$

Display $="0"$

End If

$\text{'}$ Now you will process the user input based on the input button

$\text{'}$

$\text{'}$ First, process the digits

If InputButton $="1"$ Or $\_$

InputButton $="2"$ Or $\_$

InputButton $="3"$ Or $\_$

InputButton $="4"$ Or $\_$

InputButton $="5"$ Or $\_$

InputButton $="6"$ Or $\_$

InputButton $="7"$ Or $\_$

InputButton $="8"$ Or $\_$

InputButton $="9"$ Or $\_$

InputButton $="0"$ Then

$\text{'}$ Case $1$: The current entry is an operator so you need to add a new entry for the digit

If Memory$($CurrentPos$)="+"$ Or $\_$

Memory$($CurrentPos$)="-"$ Or $\_$

Memory$($CurrentPos$)="$x$"$ Or $\_$

Memory$($CurrentPos$)="/"$ Then

$\text{'}$

$\text{'}$ Task $3$: Increasing the Size of the Calculator Memory

$\text{'}$

$\text{'}$ This code has a problem, if the calculator runs out of memory

$\text{'}$ the program will crash

$\text{'}$ Add a new number entry

CurrentPos $=$ CurrentPos $+1$

Memory$($CurrentPos$)=$ InputButton

Display $=$ Memory$($CurrentPos$)$

$\text{'}$ Case $2$: The current entry is a number so you need to add the digit at the end of it

Else

$\text{'}$

$\text{'}$ Task $2$: Extending the Calculator to Work with Multiple$-$Digit Numbers

$\text{'}$

$\text{'}$ This code is not working, you can only see single$-$digit numbers in the calculator

$\text{'}$ Add the digit to the memory array

Memory$($CurrentPos$)=$ InputButton

Display $=$ Memory$($CurrentPos$)$

End If

$\text{'}$ Then, process the $+,-,$ x$,/$ operators

ElseIf InputButton $="+"$ Or $\_$

InputButton $="-"$ Or $\_$

InputButton $="$x$"$ Or $\_$

InputButton $="/"$ Then

$\text{'}$ Beep the user if you already have an operator in the memory

If Memory$($CurrentPos$)="+"$ Or $\_$

Memory$($CurrentPos$)="-"$ Or $\_$

Memory$($CurrentPos$)="$x$"$ Or $\_$

Memory$($CurrentPos$)="/"$ Then

Beep

Else

$\text{'}$

$\text{'}$ Task $3$: Increasing the Size of the Calculator Memory

$\text{'}$

$\text{'}$ This code has a problem, if the calculator runs out of memory

$\text{'}$ the program will crash

$\text{'}$ Add a new operator entry

CurrentPos $=$ CurrentPos $+1$

Memory$($CurrentPos$)=$ InputButton

End If

$\text{'}$ Process the $=$ operator

ElseIf InputButton $="="$ Then

$\text{'}$ Calculate the total from the Memory array and

$\text{'}$ put the result in the display

ClearMemory CalcTotal$(1)$

Display $=$ Memory$(1)$

$\text{'}$ Finally, process the C $($clear$)$ operation

ElseIf InputButton $=$ "Clear" Then

$\text{'}$ Clear the current memory

ClearMemory $"0"$

Display $="0"$

End If