Perhaps, in excel select the "Home" tab then press the Alt button. Will now get a number of letters F, H, N, P, M, A, R, W and L
These are the tabs you can activate using the "SendKey" in a macro, but I'm sorry to say "SendKey" is not 100 % reliable.
To get to the sub menu for formulas start by pressing Alt button, the letter for formulas is M so pressing the Alt button and then M will open the sub menu for formulas where you can work your way down by pressing Alt + the appropriate letter.
So does your 3de party add-in have a specific letter assigned to it? If so you could try to activate it with "SendKey"
A macro for activating the formula tab would look like this:
For lower level commands you need to add more "SendKeys" with appropriate letters.
Alf
Bookmarks