Sys.Desktop.Keys("[Hold]~d");

Holds the alt and d keys...see article here for more information.

"

To simulate simultaneous pressing of several keys, use the [Hold] constant. For instance, [Hold][Win]e will launch Windows Explorer.

To deactivate [Hold], use the [Release] and [ReleaseLast] constants. [ReleaseLast] signals to TestComplete that it should simulate the releasing of the last pressed key. For instance, the string [Hold]^f[ReleaseLast]U indicates the following sequence of keypresses: pressing of CTRL, pressing of F, releasing of F, pressing of U, releasing of U and CTRL.

[Release] simulates the release of all pressed keys. For example, the string [Hold]^fU[Release] (or [Hold]^fU) indicates that TestComplete should press CTRL, then press F, then press U and then release all these keys.

"