VBA Input Function shows Run time error, type mismatch - excel

Question

I want to create a input box, and put the input into corresponding cells. But it show type mismatch.
Sub Profit_Projection()
Dim rng As Range
Dim psales As Integer
Dim msg1 As String
psales = InputBox("Please enter the predicted growth of sales next month in decimal form.", "Sales Growth", 1)
If StrPtr(psales) = 0 Then
MsgBox "You clicked Cancel button"
Exit Sub
ElseIf psales = "" Then
MsgBox "You didnt enter input"
Exit Sub
Else
Val (psales)
Range("B5") = psales * 100
If Range("B5").IsNumeric = False Then
msg1 = "The number inputted is is not integer. Please try again in decimal form."
MsgBox msg1, vbOKOnly, "Incorrect Input"
End If
End If
End Sub

Answer 1

Your main problem is that InputBox returns a String (see the official documentation), but you assign it to a numeric variable.
If the user enters some non-numeric data, you will get the type mismatch already at the psales = InputBox - statement.
If the user enters a numeric value, VBA will convert it into a number. But then you get a a type mismatch for the statement psales = "" because you cannot compare a number and a string (even if it is an empty string).
So you should assign the result of the InputBox first to a String variable and then check step by step if the entered value was okay:
Sub Profit_Projection()
Dim rng As Range
Dim psales As Integer
Dim answer
Dim msg1 As String
answer = InputBox("Please enter the predicted growth of sales next month in decimal form.", "Sales Growth", 1)
If StrPtr(answer) = 0 Then
MsgBox "You clicked Cancel button"
Exit Sub
End If
If Trim(answer) = "" Then
MsgBox "You didnt enter anything"
Exit Sub
End If
If Not IsNumeric(answer) Then
MsgBox "You didnt enter a number"
Exit Sub
End If
If CInt(answer) <> Val(answer) Then
MsgBox "You didnt enter an integer "
Exit Sub
End If
psales = Val(answer)
ActiveSheet.Range("B5") = psales * 100
End Sub