Driving a LCD from a Basic Stamp 2 microcontroller
It looks like you are trying to drive the backlight from a microcontroller pin. A typical uC pin will only source a maximum of ~20mA, your backlight may require ~100mA.  

If it was an LED based backlight you would do something like connect the backlight directly to a supply voltage through the necessary current limiting resistor.
If you wanted to switch it you would have to use an external transistor to handle the current controlled from the pin.  

However, it appears your backlight is CCFL (cold cathode fluorescent tube) based, and these require a more complex circuit to generate the high voltage required to drive them. It looks like you need ~190V.
From the datasheet:



So you will need to look into CCFL driving circuits - this LT app note is not a bad place to start reading.

Or if you don't like the idea of that, you could simply grab a display with an LED backlight, there are thousands to choose from - Displaytech make some decent cheap colour TFT screens. The SDT024BTFT is one of their latest offerings and of a similar size/resolution to your LCD.