Using Loops

I am trying to work out how to convert the following code using Loops so that after cell K2 the code goes down the column until it reaches a Row where no data exists. Anybody help. I have not used Loops before.

Thanks
Greg


Sub TravelTime()
Range("K2:K2").Select
If Range("G2").Value = "LA" And Range("J2").Value = "San Francisco" Then
Range("K2").Value = 1
ElseIf Range("G2").Value = "LA" And Range("J2").Value = "Palm Springs" Then
Range("K2").Value = 2
End If
End Sub