Create Drop-down List with Excel VBA

I want to create a drop-down list in Cell E5.

My range of values for the drop-down should come from Range(A1:A5) in Sheet2 and Range(C1:C7) in Sheet2. However, my code below is not working, it runs an error 1004 at Add xlValidateList, xlValidAlertStop, Operator:=xlBetween, Formula1:="=Sheet2!$A$1:$A$5 & Sheet2!$C$1:$C$7" I suspect it has something to do with this line...Formula1:="=Sheet2!$A$1:$A$5 & Sheet2!$C$1:$C$7" . Does anyone know how I can add two ranges into my Formula1?

Also, I dont want the blanks in the ranges to appear in the Drop-down list but .IgnoreBlank = True still shows the blanks in the drop-down list. This is my code thus far, any help is genuinely appreciated:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

If Not Intersect(Target, Range("E5")) Is Nothing Then

With Range("e5").Validation
.Add xlValidateList, xlValidAlertStop, Operator:=xlBetween, Formula1:="=Sheet2!$A$1:$A$5 & Sheet2!$C$1:$C$7"
.IgnoreBlank = True
.InCellDropdown = True
.ErrorTitle = "Warning"
.ErrorMessage = "Please select a value from the drop-down list available."
.ShowError = True

End With

End If

End Sub