Error check and if the cell is not numeric or empty loop to the next item

perhaps

   For Each cell_Check In range_ValidRows
   '''set the variables required for the method and error check'''
   
      If Application.WorksheetFunction.Count(cell_Check.Offset(, -1).Resize(4)) = 4 And Application.WorksheetFunction.CountIf(cell_Check.Offset(, -1).Resize(4), ">0") = 4 Then
         int_FirstYear = cell_Check.Value
         int_Frequency = cell_Check.Offset(0, 1).Value
         int_Spread = cell_Check.Offset(0, 2).Value
         long_Cost = cell_Check.Offset(0, -1).Value / cell_Check.Offset(0, 2).Value
         
         '''Continues with the rest of the function code
      End If
   Next cell_Check