How can make Sheet to activate in VBA from a variable? (A cell particularly) - vba

Question

I am actually quite new to VBA but I am doing some coding to streamline my office work. I understand this would be some amateur level questions to most of you but I tried to google for quite a while and I do not find satisfactory answer.
I have an excel write up that based on the inputted parameters, It should ultimately refer to the correct sheet -> copy the selected cells -> Generate an e-Mail with the body pasting the copied cells along with an attachment
I can do most of the parts, just that I cannot reference the "Correct Sheet" as a variable in my codes. Please shed some lights on for me. Thank you.
Here are most of the codes, the rest are irrelevant and too clumsy to paste all I guess.
Sub GenerateEmail()
Dim olApp As Object
Dim olMailItm As Object
Dim iCounter As Integer
Dim Dest As Variant
Dim SDest As String
Dim StrAtt1 As String
Dim rng As Range
Set rng = Nothing
On Error Resume Next
Set rng = Sheets("test").Range("A1:Q500").SpecialCells(xlCellTypeVisible)
On Error GoTo 0
If rng Is Nothing Then
MsgBox "The selection is not a range or the sheet is protected" & _
vbNewLine & "please correct and try again.", vbOKOnly
Exit Sub
End If
With Application
.EnableEvents = False
.ScreenUpdating = False
End With
Set olApp = CreateObject("Outlook.Application")
Set olMailItm = olApp.CreateItem(0)
On Error Resume Next
With olMailItm
SDest = ""
StrAtt1 = ThisWorkbook.Path & "\PDF\" & Sheets("Email_Generator").Range("B16")
.To = Worksheets("Email_Generator").Range("B14")
.CC = "Myself"
.BCC = ""
.Subject = Worksheets("Email_Generator").Range("B18")
.HTMLBody = RangetoHTML(rng)
.attachments.Add StrAtt1
.Display
End With
Set olMailItm = Nothing
Set olApp = Nothing
End Sub
Specifically, I would like this code "Sheets("test") as a Cell in Sheet "Test" that is a variable based on the paramters I have inputted in my excel so that this code will reference to the correct worksheet
Set rng = Sheets("test").Range("A1:Q500").SpecialCells(xlCellTypeVisible)
But when I identify the sheet as a named sheet e.g. Sheets("Email1"), it perfectly works, just that it cannot become a variable.
I hope this post is not too long to read because I tried to be as specific as possible. Thank you to all who reads this and tries to help. I really appreciate it.

Answer 1

This function to return the worksheet name selected by the user from an InputBox. If the user cancels or enters an invalid number then the function returns a zero length string.
Sub TestFunction()
Dim SheetName As String
Dim rng As Range
SheetName = getSheetNameFromInputBox
If Len(SheetName) = 0 Then
MsgBox Prompt:="Try Again", Title:="Invalid Sheet"
Exit Sub
End If
Set rng = Sheets(SheetName).Range("A1:Q500").SpecialCells(xlCellTypeVisible)
MsgBox rng.Address(External:=True)
End Sub
Function getSheetNameFromInputBox() As String
Dim ws As Worksheet
Dim Prompt As String
Dim result
For Each ws In ThisWorkbook.Worksheets
If Not ws.Name = "Sheet3" Then
Prompt = Prompt & ws.Index & ") " & ws.Name & vbCrLf
End If
Next
result = InputBox(Prompt:=Prompt, Title:="Enter the Worksheet number", Default:=1)
On Error Resume Next
If IsNumeric(result) Then getSheetNameFromInputBox = Worksheets(CInt(result)).Name
On Error GoTo 0
End Function