how to clear specifc portion of graphic lcd in mikroC?

hi guys, this is my first time on graphic lcd. i m using 128*64.

For example i have displayed: V = 1 volts on an alpha numeric lcd. with the following code

Lcd_Out(1, 1, "V=<space><space>volts"); it would appear like thi on lcd:
V= volts

if suppose int Vdd=1 than

Lcd_Chr(1,3Vdd+48);

which gives the result
V=1 Volts on lcd.
now if Vdd = 2 than

Lcd_Chr(1,3Vdd+48);
which gives the result
V=2 Volts on lcd.

Notice that i have replaced 1 by 2 and i haven't cleared the line or whole screen. if i clear the screen every time the "Vdd" updates say every 200ms the the lcd screen would be flickering.

Same question is for Graphic LCD. How to i replace a single character or digit. Glcd_Fill(0x00); dosent help since it clears all the screen.
similarly if i do this
Glcd_Write_char("A", 0, 0, 2);
and than
Glcd_Write_char("B", 0, 0, 2);
it wont work either as A and B jumbles up.

any idea?

many ideas.
but you first have to clear upi questions about the s/w ( where did you get Lcd_Chr() and Glcd_Write_char() from ) and also which 128x64 you are using

these are the builtin libraries of mikroc pro for pic. and i am using jhd12864e lcd module.

Dear Friends,
I am Luong, i'm doing Graphic LCD and PIC C30,
I need libraries to display,
Could you help me?