Homemade TM1 reports can get quite convoluted and users might get a hard time updating them as it is difficult to tell where some TM1 formulas are pointing to.
The excel formula auditing toolbar can be useful in such situations.

• right click next to the top bar to bring up the bars menu
• select "Formula Auditing" bar

AsciiOutput can help tracking what values are being used during execution of your TI processes.

use:

AsciiOutput('\\path\to\debug.cma',var1,var2,NumberToString(var3));

Keep in mind Asciioutput limitations: