Thanks for replying Bob.

The code to draw the button and assign are as follows :

With ActiveSheet.Buttons.Add(Range("A2:H2").Width, Range("I1:I2").Height,
Range("I2").Width, Range("I4").Top)
.Name = "ModifySheet"
.Caption = "Modify Worksheet"
.OnAction = "ModifyMenu"
End With

The problem is that when I click the button its looking for 'ModifyMenu' in
the master file not the activework book. To me this looks more or less the
same as the sample and various other postings I've read.

If the button is in the master file I can assign the other way e.g

Selection.OnAction = "'H810-26011006_Oct-05.xls'!ModifyMenu"

So a really dumb solution would be draw the button in file_01 etc cut and
paste it into master, use the line above which works, then cut and paste it
back to file_01. This works but it seems a very silly way of doing it :-\

The question is, how from master can I draw a button and assign code in
file_01 ? As per my original examples they all link back to master which
doesn't have the code even.... I've been pulling my hair out on this one to
say the least !!

TIA