How to Hold Down Shift Key Indefinitely?

[BAN]

Is there a way to simulate the holding down of the Shift key for an
extended period of time?

Basically, I need to press and hold the Shift key while I execute
another program. The program behaves differently depending on whether
or not the Shift key is pressed when the program is run.

The "SendKeys" command does not work for me because it is used only as
a modifier for the next character.

A command such as ShiftDown, then later ShiftUp would fit my needs
exactly.

Any ideas?

-BAN