Hi Deca,
You can use the CmdExecuteSync method of the DIAdem.TOCommand interface to set the value of a text channel. For example passing the string "CHT(1,1) := 'test'" as a parameter to the CmdExecuteSync method will set the 1st row of the 1st channel to "test". Please refer to the DIAdem help for more documentation on the CHT function.
I hope this helps! Please post back if I wasn't clear enough in explaining how to do this or if you have any problems getting it to work.
Regards,
Sarah Miracle
National Instruments