Date issue in Webi 4.0

Hello All,

I am facing issue with the date. I am getting  #error. Please find the formula

="For the Period "+FormatDate([z_Prompted Begin Date] ; "MM/dd/yyyy")+ " -- "+FormatDate([z_Prompted End date] ; "MM/dd/yyyy")

where

z_Prompted Begin Date  =ToDate((UserResponse([Build & Activation] ;"Begin Date(mm/dd/yyyy)")) ;"MM/dd/yyyy")

[z_Prompted End date] = =ToDate((UserResponse([Build & Activation] ;"End Date(mm/dd/yyyy)")) ;"MM/dd/yyyy")

When i check sysntax for all the formula, it says correct but i get # Error.

Please let me know.

Best Regards

Sandy