If that is not an option then here is some code that may help...
Sub Inc_Num()
Dim EndRow As Long
Dim rCell As Range
Dim incNum As Long
' this assumes you want the incremented numbers in column "A" and
' that your true/false column is solid with data and is column "D".
' it starts at "D2".
incNum = 1
EndRow = Sheet1.Range("D" & Rows.Count).End(xlUp).Row
For Each rCell In Sheet1.Range("D2:D" & EndRow).Cells
If rCell.Value = True Then
rCell.Offset(, -3).Value = incNum
incNum = incNum + 1
End If
Next
End Sub
Hope this helps