izzit prosible to let GetFillName point to my CasherTxt in form . and get amount from the form. the amount is a dsum amount from another table.

You are getting the error because GetFillName is the name of a variable.
Remove the Me.

MsgBox GetFillName

MsgBox GetFillName = CasherTxt
i try to get value in CasherTxt = a number (exp: 123)

Dim GetTableName, GetAmount, temp
    GetTableName = DLookup("TableName", "Cash_Table_T", "TableID = " & SelectionCombo) 'CasherTxt
    
    temp = Nz(DSum("[Amount]", GetTableName, "InputDate>=#" & [DateFrom] & "# AND InputDate<=#" & [DateUntil] + 1 & "#"), 0)
    MsgBox temp

if is dsum in vba. yes i get the vable from table.
i keep think for few day izzit we can making try to pull the value from GetFillName
if really not posible please let me know

You can't msgbox with an = sign.

Honestly your setup here is hard to read. What are you trying to do?

If you are trying to set a value with a dlookup it should be something like this
CasherTxt=DLookup("YourFieldName", "YourTableName", "YourID=" & YourField)