Your code, as written, will not process appropriately. Also, check boxes do not reside in cells. The essentially 'hover' above the worksheet. They can be sized and positioned to appear as if they reside in the cells.
Here is a method to automatically add 75 checkboxes to a worksheet, and make them appear to be in rows 1-75. This process assumes that the row height is the standard Excel default of 12.75. You will have to rename the check box text and size column A to the appropriate width to make them appear to be in the cell.
Copy the following event handler to the clipboard:
Private Sub Worksheet_Calculate()
Dim i, LastRow
LastRow = Range("IU" & Rows.Count).End(xlUp).Row
Application.EnableEvents = False
For i = 1 To LastRow
If Cells(i, "IU").Value = "T" Then
Cells(i, "B").Value = Date
ElseIf Cells(i, "IU").Value = "F" Then
Cells(i, "B").Value = ""
End If
Next
Application.EnableEvents = True
End Sub
Select the worksheet to contain the check boxes and right click the sheet tab.
Select 'View Code'
Paste the event handler code into the sheet module editing area to the right.
In the menus at the top of the VBE, select INSERT > MODULE
Copy the following two macros to the clipboard and paste them into the newly created module:
Sub Assign_Linked_Cells()
On Error Resume Next
Application.ScreenUpdating = False
Dim i
For i = 1 To 75
ActiveSheet.Shapes("check box " & i).Select
With Selection
.LinkedCell = "IV" & i
End With
Cells(i, "IU").Formula = "=IF(IV" & i & "=TRUE,""T"",""F"")"
Next
Columns("IU:IV").EntireColumn.Hidden = True
End Sub
Sub InsertCkBoxes()
Dim setTop, i
setTop = 0
For i = 1 To 75
Set cb = ActiveSheet.Shapes. _
AddFormControl(xlCheckBox, 0, setTop, 75, 1)
cb.ControlFormat.LinkedCell = "IV" & i
setTop = setTop + 12.74
Next
Assign_Linked_Cells
End Sub
Close the VBE and return to the worksheet to contain the 75 check boxes.
Press ALT + F8
When the Macros window opens, select the InsertCkBoxes macro and click 'RUN'.
Close the Macros window.
Widen column A to contain the checkboxes.
Click a check box and the current date will be entered into column B in the same row as the check box 'appears' to be in.
Edit: If your row height is not 12.75, you can modify the code to suit your row height. For example, if your row height is 15.00, change this line:
setTop = setTop + 12.74
to
setTop = setTop + 14.99