"Run-Time Error '13' Type Mismatch"

I am getting a "Run-Time Error '13' Type Mismatch" for the following code and I don't know what that means.

Any help?

'       Display Product Mix Data
        For X = 8 To neSales.Cells(8, 2).End(xlDown).Row
        If neSales.Cells(X, 2).Value = "%" _
        And Month(neSales.Cells(X, 1).Value) & "/" _
        & Day(neSales.Cells(X, 1).Value) & "/" _
        & Year(neSales.Cells(X, 1).Value) = SelectMonth.Value _
        Then
            Sales.PM1220.Value = neSales.Cells(X, 3).Value
            Sales.PM1630.Value = neSales.Cells(X, 4).Value
            Sales.PM2040.Value = neSales.Cells(X, 5).Value
            Sales.PM3050.Value = neSales.Cells(X, 6).Value
            Sales.PM4070.Value = neSales.Cells(X, 7).Value
            Sales.PM100M.Value = neSales.Cells(X, 8).Value
            Sales.PMTotal.Value = neSales.Cells(X, 9).Value
            Exit For
        Else
        End If
    Next