Left Margin error

[ireeve]

When I try to use VBA to change left margin in Word I get an error, if I simply drag from the ruler - no problem.
But I want to use something like
ActiveDocument.Sections(28).PageSetup.LeftMargin = 72

Run time error 5518
Increasing left margin causes first column to become too narrow some....

I have only one column

Help please

Update 1:
There are many sections in the document, I am only concerened in this example with section 28.


Its A4 Portrait Right margin normal.
The error message is the 5518 above.