Too bad you felt the type of DB type/connectivity, and the data type of {TEMP_ORDER_HEADER.BVSUBTOTAL} unimportant to post, it may prove key to the solution.
So this doesn't show that you used the INT function anywhere...
Anyway, if they are numerics, try:
if {TEMP_ORDER_HEADER.BVSUBTOTAL} > 100 then
IDAutomationFontEncoderCode128 ({TEMP_ORDER_HEADER.NUMBER} & totext({TEMP_ORDER_HEADER.BVSUBTOTAL},"",0,),0 )
else IDAutomationFontEncoderCode128 ({TEMP_ORDER_HEADER.NUMBER},0)
If it's a string type, try:
if {TEMP_ORDER_HEADER.BVSUBTOTAL} > 100 then
IDAutomationFontEncoderCode128 ({TEMP_ORDER_HEADER.NUMBER} & totext(val({TEMP_ORDER_HEADER.BVSUBTOTAL}),"",0),0 )
else IDAutomationFontEncoderCode128 ({TEMP_ORDER_HEADER.NUMBER},0)
-k