The inelegance of most number application scripts is a minor bugbear of mine. If you were to change the filenames of the textures to be the same as the digit (ie. 0.paa, 1.paa etc.) you might use the following:
_unit = _this select 0
_number = [0, 0, 0]
goto "getnum"
#loop
~1
? time < _mytime: goto "apply"
? (alive _unit): goto "loop"
exit
#apply
call format ["_unit setObjectTexture [0,{\modem_adats\n\%1.paa}]", _number select 0]
call format ["_unit setObjectTexture [1,{\modem_adats\n\%1.paa}]", _number select 1]
call format ["_unit setObjectTexture [2,{\modem_adats\n\%1.paa}]", _number select 2]
_mytime = 1 + time
goto "loop"
#getnum
_ran = random 10
_ran = _ran - (_ran mod 1)
_number set [0, _ran]
_ran = random 10
_ran = _ran - (_ran mod 1)
_number set [1, _ran]
_ran = random 10
_ran = _ran - (_ran mod 1)
_number set [2, _ran]
goto "apply"
Currently the numerals are chosen at random, but any other method should work just as well.