Excel VBA script to check whether cell value appears in array of other cells. If not, show a MsgBox and force the user to re-input

Question

VBA beginner here. I apologize for not being able to provide a code snippet, but I'm seeking a script that works as follows:

1. Check whether the value inputted in a cell (say A1) appears in an array of cells (say B1:B100).
2. If the value inputted to A1 does NOT appear in B1:B100, show a MsgBox with Retry/Cancel buttons that warns the user that their input is invalid.
3. If the user selects Retry, RE-ACTIVATE cell A1 so that the user must re-input a different value. If the user selects Cancel, leave cell A1 blank and exit the cell.

I am seeking a VBA solution only, NOT Excel's built-in Data Validation feature (for a number of reasons).

Thank you everyone!

Answer 1

Try this for a starting point. If you insert a "Shape" and assign this macro to it. The shape can be used as a button to run the macro when clicked on.

Sub Macro1()

Dim v1 As Variant
Dim loop1, msgbutton As Long

v1 = Cells(1, 1).Value 'read the value in cell A1

For loop1 = 1 To 100
    'compare v1 with cells range B1 to B100
    If v1 = Cells(loop1, 2).Value Then Exit For
Next loop1

'if there is a match the loop will exit before reaching 101
If loop1 > 100 Then
    'no match so make a message box
    msgbutton = MsgBox("The data is invalid.", 5, "Box Title")
    If msgbutton = 4 Then 'retry
        Cells(1, 1).Value = Empty
        Cells(1, 1).Select
    Else 'cancel
        Cells(1, 1).Value = Empty
    End If
Else 'it's a match
    Stop 'your code here
End If

End Sub