Modifying AutoShape adjustments
Problem
You want to modify the "yellow diamond" adjustments on an autoshape but it's impossible to do the job precisely because the adjustments don't snap to the grid or to guidelines.
Solution
VBA to the rescue.
This macro shows the "adjustments" available for the currently selected shape and the current value of each:
Sub ShowAdjustments()
Dim oSh As Shape
Dim lCount As Long
Set oSh = ActiveWindow.Selection.ShapeRange(1)
With oSh
For lCount = 1 To .Adjustments.Count
MsgBox "Adjustment " & CStr(lCount) _
& vbCrLf & CStr(.Adjustments(lCount))
Next
End With
End Sub
Then you can use this to modify the adjustments:
Sub SetAdjustments()
Dim oSh As Shape
Set oSh = ActiveWindow.Selection.ShapeRange(1)
With oSh
.Adjustments(1) = 0.66
.Adjustments(2) = 0.66
' And so on for add'l adjustments
End With
End Sub
See How do I use VBA code in PowerPoint? to learn how to use this example code.