CustomLength Method
Specifies that the first segment of the callout line (the segment attached to the text callout box) retain a fixed length whenever the callout is moved. Use the AutomaticLength method to specify that the first segment of the callout line be scaled automatically whenever the callout is moved. Applies only to callouts whose lines consist of more than one segment (types msoCalloutThree and msoCalloutFour).
expression.CustomLength(Length)
expression Required. An expression that returns a CalloutFormat object.
Length Required Single. The length of the first segment of the callout, in points.
Remarks
Applying this method sets the AutoLength property to False and sets the Length property to the value specified for the Length argument.
Example
This example toggles between an automatically scaling first segment and one with a fixed length for the callout line for shape one on myDocument. For the example to work, shape one must be a callout.
Set myDocument = Worksheets(1)
With myDocument.Shapes(1).Callout
If .AutoLength Then
.CustomLength 50
Else
.AutomaticLength
End If
End With