$-$ Prepare a userform where the input fields are

o Book Name $($text$)$

o Book Author $($text$)$

o ISBN No $($unique number$)$

o Selling Price $($Currency between $$5\mathrm{.}00$ and $$100\mathrm{.}00)$

o Last Months Sales Quantity $($integer between $100$ and $1500)$

$-$ In the form there should be Save Data, Close Form buttons. Each record should be added to a new line.

$-$ Prepare a second form $($reachable from the first form$)$ where

o there are summarizing fields where you calculate the total monthly revenue $/$ total quantity sold $/$ best selling book$$s title $/$ revenue $\%$ of best selling book to total sales

o You can display the details of a book when you enter the ISBN no $($so there will be a field where you enter ISBN no$.$ and when you click it$,$ it should display all the details about that book$)$

$-$ Fill with at least $10$ book data $($you can randomly give numbers and names...$)$Private Sub CommandButton$1\_$Click$()$

Dim iRow As Long

Dim ws As Worksheet

Set ws $=$ Worksheets$("$Sheet$1")\text{'}$ Ensure sheet name matches exactly, including case

$\text{'}$ Find first empty row in database

iRow $=$ ws$.$Cells.Find$($What:$="*",$ SearchOrder:$=$xlRows, SearchDirection:$=$xlPrevious, LookIn:$=$xlValues$).$Row $+1$

$\text{'}$ Check for a book name $($assuming TextBox$1$ is for book name$)$

If Trim$($Me$.$TextBox$1.$Value$)=""$ Then

Me$.$TextBox$1.$SetFocus

MsgBox "Please enter a Book Name"

Exit Sub

End If

$\text{'}$ Check for ISBN number $($assuming TextBox$3$ is for ISBN$)$

If Trim$($Me$.$TextBox$3.$Value$)=""$ Then

Me$.$TextBox$3.$SetFocus

MsgBox "Please enter an ISBN Number"

Exit Sub

End If

$\text{'}$ Check if ISBN already exists

If WorksheetFunction.CountIf$($ws$.$Range$("$C:C$"),$ Me$.$TextBox$3.$Value$)>0$ Then

Me$.$TextBox$3.$SetFocus

MsgBox "ISBN already exists!"

Exit Sub

End If

$\text{'}$ Copy the data to the database

With ws

$.$Cells$($iRow$,1).$Value $=$ Me$.$TextBox$1.$Value $\text{'}$ Book Name

$.$Cells$($iRow$,2).$Value $=$ Me$.$TextBox$6.$Value $\text{'}$ Book Author

$.$Cells$($iRow$,3).$Value $=$ Me$.$TextBox$3.$Value $\text{'}$ ISBN

$\text{'}$ Validate and assign Selling Price

If IsNumeric$($Me$.$TextBox$4.$Value$)$ And Val$($Me$.$TextBox$4.$Value$)>=5$ And Val$($Me$.$TextBox$4.$Value$)<=100$ Then

$.$Cells$($iRow$,4).$Value $=$ Me$.$TextBox$4.$Value

Else

MsgBox "Selling Price must be between $$5$ and $$100"$

Me$.$TextBox$4.$SetFocus

Exit Sub

End If

$\text{'}$ Validate and assign Last Month's Sales Quantity

If IsNumeric$($Me$.$TextBox$5.$Value$)$ And Val$($Me$.$TextBox$5.$Value$)>=100$ And Val$($Me$.$TextBox$5.$Value$)<=1500$ Then

$.$Cells$($iRow$,5).$Value $=$ Me$.$TextBox$5.$Value

Else

MsgBox "Sales Quantity must be between $100$ and $1500"$

Me$.$TextBox$5.$SetFocus

Exit Sub

End If

wb$.$Save

End With

$\text{'}$ Clear the data

Me$.$TextBox$1.$Value $=""$

Me$.$TextBox$6.$Value $=""$

Me$.$TextBox$3.$Value $=""$

Me$.$TextBox$4.$Value $=""$

Me$.$TextBox$5.$Value $=""$

MsgBox "Data saved successfully!"

End Sub

Private Sub CommandButton$2\_$Click$()$

Unload Me

End Sub

Private Sub TextBox$4\_$Enter$()$

MsgBox "Price Between $$5-$ $$100"$

End Sub

Private Sub TextBox$5\_$Enter$()$

MsgBox "Quantity Between $100-1500"$

End Sub we write the vba code like this but it give "error $91"$ on excel. can you tell me what the mistake is and rewrite the code. Note: textbox$6$ refers the textcode$2$ in our code