Please help! loop/Insert text in first blank space

Hi all,

I hope someone can help it is driving me insane!!

I am using Ron de Bruin Popup menus to form an invoice by selecting the following Sub test macros, however I am trying to loop to the next blank cell, IE if cells b21:j21 are already filled that it loops to b22:j21and inserts the text in there.

 Sub TestMacro1()
 Range("b21").Select
 ActiveCell.FormulaR1C1 = "Peugeot 206"
 Range("c21").Select
 ActiveCell.FormulaR1C1 = "1 Previous owner"
 Range("h21").Select
 ActiveCell.FormulaR1C1 = "£3,195.00"
 Range("j21").Select
 ActiveCell.FormulaR1C1 = "Blue"
 End Sub

 Sub TestMacro2()
 Range("b21").Select
 ActiveCell.FormulaR1C1 = "Ford KA"
 Range("c21").Select
 ActiveCell.FormulaR1C1 = "2 Previous owners"
 Range("h21").Select
 ActiveCell.FormulaR1C1 = "£4,195.00"
 Range("j21").Select
 ActiveCell.FormulaR1C1 = "Black"
 End Sub

I have tried lots of loop formula from different sites however none really work

Many thanks for your help
Paul