prevent c4 from shifting itself into 3rd

how can i prevent my c4 from shifting itself into 3rd on its own? i wanna control the 2-3 shift point. i know i can get a manual vb but i need to fix this problem in 5 days for the last t&t of the year. any suggestions?
[addsig]

ya,shift it manually
[addsig]

i allways shift it manually at 6400 rpm from 1-2 but when i try to hold it in 2nd to 6400 rpm it will automatically shift itself into 3rd at 5-5500 rpm. that is what my problem is.
[addsig]

Transgo stage two shift kit, locks out 2-3 shift with the handle in the 2nd postion

I suspect you have a green dot valvebody..Someone else might be able to give the exact method but it goes something like shift 1 to 2 then back to one to hold it in 2nd then shift to 3rd.