change text style

[chunyuran]

I am working on changing text style. 

 In AutoCAD, entities containing text style including " text, mtext, attdef, attrib, dimension, block reference". I want to change any entities with specified text style in a dwg.

1 For acdbdimension,  after changing the text style in the dimension style, the acdbdimension entities in the dwg automatically changed their text. But for acdbBlockReference, after changing the text style of entities in the block defintion,  block references in the dwg didn't change their text apperance at all.  I'm sure the change for block definition is valid,  because when insert  the text style changed block by hand, i got the wanted drawing. 

Is there some api to ensure all previous inserted block reference to change their text style?

2 I don't want to interate all entities in the model space, for i feel it's not an efficient way, even if I am not sure of that.  For changing all text and mtext's text style, i want to just change their text style's file name and big font file name. the same problem come up,  all previously inserted text and mtext didn't change.

Any advice will be appreciated. 

[chunyuran]

REGEN made it work.