Nadya,
I didn't follow whole the thread and may be I'll say something stupid, what if:

.cboEmployees.rowsourcetype = 3
.cboEmployees.rowsource = ;
			"SELECT distinct cEmpName, cUserID " + ;
			"FROM " + m.tcEmployeeAlias + ;
			" INTO CURSOR c_AllEmployees " + ;
			"ORDER BY 1"
if not empty(.oBizObj.cEmployeeID)
   .cboEmployees.value = .oBizObj.cEmployeeID
   .cboEmployees.controlsource = .oBizObj.cUserID
else
   .cboEmployees.value = .null. && we want to start with no selection
   .cboEmployees.controlsource = ""
   * .cboEmployees.ListIndex = 0
endif

And then in InterActiveChange event of the Combo:

IF NOT ISNULL(this.Value) AND NOT EMPTY(this.Value) AND EMPTY(this.ControlSource)
   LOCAL lComboValue
   lComboValue = this.Value
   this.controlsource = xxx.oBizObj.cUserID
   this.Value = lComboValue
ENDIF

(not tested)