Sorry about that... try:
Code:
=SUM(IF($A$3:$A$11="Business Support",(NETWORKDAYS(IF($D$1>$B$3:$B$11,$D$1,$B$3:$B$11),IF(EOMONTH($D$1,0)<$C$3:$C$11,EOMONTH($D$1,0),$C$3:$C$11))),0))
Confirmed with CTRL+SHIFT+ENTER
You can replace "Business Support" with a reference cell containing that text string...