Bitmap-Number
This property defines which image among the ones in the bitmap strip referenced by the 
Bitmap-Handle property is to be displayed in the page identified by the 
Tab-Index property.
When the values are enclosed between parentheses, the 
Tab-Index property is ignored, the 1st value refers to the 1st Tab, the 2nd value refers to the 2nd Tab and so on.
 
Example - Modify a tab-control to assign a bitmap number to each page
procedure division. ...   modify screen-1-tc-1          tab-to-add ( "Page-1" "Page-2")          bitmap-number ( 3 2)          . ...  |