How to start and stop a loop base on condition.

Hi,

I have a piece of code that put a check in all checkbox
in column B from row 5 to row 50 but in column C, I have
data from row 5 to 38. I want the macro to stop at row
38 in column B. When the cell in column C is empty stop
putting checks in column B.

How can I make this macro Check all checkbox down column B
and stop when column C is empty..

How do I add a loop to stop when the cell in column C is empty?

Private Sub CommandButton1_Click()

Dim CB As Variant
For Each CB In ActiveSheet.CheckBoxes
CB.Value = False
Next
End Sub

.....A.......B............C...............
....1S......X............Ms..............
....1M......X............Mr. &. Mrs....
....1S......X............Ms..............
....1S......X............ ...............