point to a subform control within query criteria

[abo fahad]

hi there!

i have two sub forms within a main form
let say frmMain, frmSub1, frmSub2
frmSub1 contains BillFromDate and BillToDate
frmSub2 displays bill data between these two dates
(this mean that the second form (frmSub2) based on a query which contains on BillDate field criteria the following statement,
"Between [Forms]![frmMain]![frmSub1 ].[Form]![BillFromDate] And [Forms]![frmMain]![frmSub1 ].[Form]![BillToDate]")
when i run the program it allwase ask me to enter these two parameters? while it's already contains dates.

may be this is not the right way to point to a parameter in a subform?

pls. help