For entering data you can use a TextBox and a Button, then when the user clicks the button verify there is a number in the TextBox using IsNumeric(). About the Array, (assuming it's not a fixed length array) you can initialize it like ReDim ArrName(0) in Form_Load event. Then you need to verify if the number has been entered before, use a FOR / NEXT loop to to compare every item inside the array with this number. Finally, if it's not present you can add it using ReDim Preserve ArrName(UBound(ArrName) + 1) and then ArrName(UBound(ArrName)) = TheNumber. Try this and send feedback for every trouble it could arise.