Call Transaction Background Mode

Hi experts,

I using call transaction for z tcode. This is working normaly but in background mode not working. Because call transaction can not transporting screen element's values. Sample :

FNAM           |      FVAL

P_CONTR            00123141232

In foreground : p_contr = 00123141232 in z tcode but in background p_contr is initial. So i can not transporting values in background.

Can you help me please ?

Thank you / regards.