need help in writing Query customer exit convert lower to upper case

hi guys . i have a scenario.

our data is converted in to upper case from BW. in the query designer i need to create a variable, so when the user click on selection option and enter anything in lower case, it will convert it to upper case and do the search.

i have a created a customer exit variable.. ZPROJECTSEL

i am writing an abap code.

WHEN 'ZPROJECTSEL'.

CLEAR l_s_range.

DATA: t(10) TYPE c . ** do i need to declare a variable to hold the converted upper case data?

if i_step = 2.

• this is where i am lost****

t = ZPROJECTSEL.

TRANSLATE t TO UPPER CASE.

zprojectsel = t.

so any ideas in understanding variable exit would be helpful.

thanks